freespec
Facilitates a “behavior-driven” style of development (BDD), in which tests
are nested inside text clauses denoted with the dash operator (-).
Implementation trait for class AnyFreeSpec, which
facilitates a “behavior-driven” style of development (BDD),
in which tests are nested inside text clauses denoted with the dash
operator (-).
Implementation trait for class AnyFreeSpec, which
facilitates a “behavior-driven” style of development (BDD),
in which tests are nested inside text clauses denoted with the dash
operator (-).
AnyFreeSpec is a class, not a trait,
to minimize compile time given there is a slight compiler overhead to
mixing in traits compared to extending classes. If you need to mix the
behavior of AnyFreeSpec into some other class, you can use this
trait instead, because class AnyFreeSpec does nothing more than
extend this trait and add a nice toString implementation.
See the documentation of the class for a detailed
overview of AnyFreeSpec.
Enables testing of asynchronous code without blocking,
using a style consistent with traditional AnyFreeSpec tests.
Enables testing of asynchronous code without blocking,
using a style consistent with traditional AnyFreeSpec tests.
Recommended Usage:
AsyncFreeSpec is intended to enable users of AnyFreeSpec
to write non-blocking asynchronous tests that are consistent with their traditional AnyFreeSpec tests.
Note: AsyncFreeSpec is intended for use in special situations where non-blocking asynchronous
testing is needed, with class AnyFreeSpec used for general needs.
|
Given a Future returned by the code you are testing,
you need not block until the Future completes before
performing assertions against its value. You can instead map those
assertions onto the Future and return the resulting
Future[Assertion] to ScalaTest. The test will complete
asynchronously, when the Future[Assertion] completes.
Here's an example AsyncFreeSpec:
package org.scalatest.examples.asyncfreespec
import org.scalatest.freespec.AsyncFreeSpec
import scala.concurrent.Future
class AddSpec extends AsyncFreeSpec {
def addSoon(addends: Int*): Future[Int] = Future { addends.sum }
"addSoon" - {
"will eventually compute a sum of passed Ints" in {
val futureSum: Future[Int] = addSoon(1, 2)
// You can map assertions onto a Future, then return
// the resulting Future[Assertion] to ScalaTest:
futureSum map { sum => assert(sum == 3) }
}
}
def addNow(addends: Int*): Int = addends.sum
"addNow" - {
"will immediately compute a sum of passed Ints" in {
val sum: Int = addNow(1, 2)
// You can also write synchronous tests. The body
// must have result type Assertion:
assert(sum == 3)
}
}
}
In an AsyncFreeSpec you write a test with a string followed by in and the body of the
test in curly braces, like this:
"will eventually compute a sum of passed Ints" in {
// ...
}
You can nest a test inside any number of description clauses, which you write with a string followed by a dash character and a block, like this:
"addSoon" - {
// ...
}
You can nest description clauses as deeply as you want. Because the description clause is denoted with an operator, not
a word like should, you are free to structure the text however you wish.
In short, you structure an AsyncFreeSpec exactly like a AnyFreeSpec, but with
tests having result type Assertion or Future[Assertion]. For more examples
of structure, see the documentation for AnyFreeSpec.
Starting with version 3.0.0, ScalaTest assertions and matchers have result type Assertion.
The result type of the first test in the example above, therefore, is Future[Assertion].
For clarity, here's the relevant code in a REPL session:
scala> import org.scalatest._
import org.scalatest._
scala> import Assertions._
import Assertions._
scala> import scala.concurrent.Future
import scala.concurrent.Future
scala> import scala.concurrent.ExecutionContext
import scala.concurrent.ExecutionContext
scala> implicit val executionContext = ExecutionContext.Implicits.global
executionContext: scala.concurrent.ExecutionContextExecutor = scala.concurrent.impl.ExecutionContextImpl@26141c5b
scala> def addSoon(addends: Int*): Future[Int] = Future { addends.sum }
addSoon: (addends: Int*)scala.concurrent.Future[Int]
scala> val futureSum: Future[Int] = addSoon(1, 2)
futureSum: scala.concurrent.Future[Int] = scala.concurrent.impl.Promise$DefaultPromise@721f47b2
scala> futureSum map { sum => assert(sum == 3) }
res0: scala.concurrent.Future[org.scalatest.Assertion] = scala.concurrent.impl.Promise$DefaultPromise@3955cfcb
The second test has result type Assertion:
scala> def addNow(addends: Int*): Int = addends.sum addNow: (addends: Int*)Int scala> val sum: Int = addNow(1, 2) sum: Int = 3 scala> assert(sum == 3) res1: org.scalatest.Assertion = Succeeded
When AddSpec is constructed, the second test will be implicitly converted to
Future[Assertion] and registered. The implicit conversion is from Assertion
to Future[Assertion], so you must end synchronous tests in some ScalaTest assertion
or matcher expression. If a test would not otherwise end in type Assertion, you can
place succeed at the end of the test. succeed, a field in trait Assertions,
returns the Succeeded singleton:
scala> succeed res2: org.scalatest.Assertion = Succeeded
Thus placing succeed at the end of a test body will satisfy the type checker:
"will immediately compute a sum of passed Ints" - {
val sum: Int = addNow(1, 2)
assert(sum == 3)
println("hi") // println has result type Unit
succeed // succeed has result type Assertion
}
An AsyncFreeSpec's lifecycle has two phases: the registration phase and the
ready phase. It starts in registration phase and enters ready phase the first time
run is called on it. It then remains in ready phase for the remainder of its lifetime.
Tests can only be registered with the it method while the AsyncFreeSpec is
in its registration phase. Any attempt to register a test after the AsyncFreeSpec has
entered its ready phase, i.e., after run has been invoked on the AsyncFreeSpec,
will be met with a thrown TestRegistrationClosedException. The recommended style
of using AsyncFreeSpec is to register tests during object construction as is done in all
the examples shown here. If you keep to the recommended style, you should never see a
TestRegistrationClosedException.
AsyncFreeSpec extends AsyncTestSuite, which provides an
implicit scala.concurrent.ExecutionContext
named executionContext. This
execution context is used by AsyncFreeSpec to
transform the Future[Assertion]s returned by each test
into the FutureOutcome returned by the test function
passed to withFixture.
This ExecutionContext is also intended to be used in the tests,
including when you map assertions onto futures.
On both the JVM and Scala.js, the default execution context provided by ScalaTest's asynchronous
testing styles confines execution to a single thread per test. On JavaScript, where single-threaded
execution is the only possibility, the default execution context is
scala.scalajs.concurrent.JSExecutionContext.Implicits.queue. On the JVM,
the default execution context is a serial execution context provided by ScalaTest itself.
When ScalaTest's serial execution context is called upon to execute a task, that task is recorded
in a queue for later execution. For example, one task that will be placed in this queue is the
task that transforms the Future[Assertion] returned by an asynchronous test body
to the FutureOutcome returned from the test function.
Other tasks that will be queued are any transformations of, or callbacks registered on, Futures that occur
in your test body, including any assertions you map onto Futures. Once the test body returns,
the thread that executed the test body will execute the tasks in that queue one after another, in the order they
were enqueued.
ScalaTest provides its serial execution context as the default on the JVM for three reasons. First, most often
running both tests and suites in parallel does not give a significant performance boost compared to
just running suites in parallel. Thus parallel execution of Future transformations within
individual tests is not generally needed for performance reasons.
Second, if multiple threads are operating in the same suite
concurrently, you'll need to make sure access to any mutable fixture objects by multiple threads is synchronized.
Although access to mutable state along
the same linear chain of Future transformations need not be synchronized,
this does not hold true for callbacks, and in general it is easy to make a mistake. Simply put: synchronizing access to
shared mutable state is difficult and error prone.
Because ScalaTest's default execution context on the JVM confines execution of Future transformations
and call backs to a single thread, you need not (by default) worry about synchronizing access to mutable state
in your asynchronous-style tests.
Third, asynchronous-style tests need not be complete when the test body returns, because the test body returns
a Future[Assertion]. This Future[Assertion] will often represent a test that has not yet
completed. As a result, when using a more traditional execution context backed by a thread-pool, you could
potentially start many more tests executing concurrently than there are threads in the thread pool. The more
concurrently execute tests you have competing for threads from the same limited thread pool, the more likely it
will be that tests will intermitently fail due to timeouts.
Using ScalaTest's serial execution context on the JVM will ensure the same thread that produced the Future[Assertion]
returned from a test body is also used to execute any tasks given to the execution context while executing the test
body—and that thread will not be allowed to do anything else until the test completes.
If the serial execution context's task queue ever becomes empty while the Future[Assertion] returned by
that test's body has not yet completed, the thread will block until another task for that test is enqueued. Although
it may seem counter-intuitive, this blocking behavior means the total number of tests allowed to run concurrently will be limited
to the total number of threads executing suites. This fact means you can tune the thread pool such that maximum performance
is reached while avoiding (or at least, reducing the likelihood of) tests that fail due to timeouts because of thread competition.
This thread confinement strategy does mean, however, that when you are using the default execution context on the JVM, you
must be sure to never block in the test body waiting for a task to be completed by the
execution context. If you block, your test will never complete. This kind of problem will be obvious, because the test will
consistently hang every time you run it. (If a test is hanging, and you're not sure which one it is,
enable slowpoke notifications.) If you really do
want to block in your tests, you may wish to just use a
traditional AnyFreeSpec with
ScalaFutures instead. Alternatively, you could override
the executionContext and use a traditional ExecutionContext backed by a thread pool. This
will enable you to block in an asynchronous-style test on the JVM, but you'll need to worry about synchronizing access to
shared mutable state.
To use a different execution context, just override executionContext. For example, if you prefer to use
the runNow execution context on Scala.js instead of the default queue, you would write:
// on Scala.js
implicit override def executionContext =
org.scalatest.concurrent.TestExecutionContext.runNow
If you prefer on the JVM to use the global execution context, which is backed by a thread pool, instead of ScalaTest's default serial execution contex, which confines execution to a single thread, you would write:
// on the JVM (and also compiles on Scala.js, giving
// you the queue execution context)
implicit override def executionContext =
scala.concurrent.ExecutionContext.Implicits.global
By default (unless you mix in ParallelTestExecution), tests in an AsyncFreeSpec will be executed one after
another, i.e., serially. This is true whether those tests return Assertion or Future[Assertion],
no matter what threads are involved. This default behavior allows
you to re-use a shared fixture, such as an external database that needs to be cleaned
after each test, in multiple tests in async-style suites. This is implemented by registering each test, other than the first test, to run
as a continuation after the previous test completes.
If you want the tests of an AsyncFreeSpec to be executed in parallel, you
must mix in ParallelTestExecution and enable parallel execution of tests in your build.
You enable parallel execution in Runner with the -P command line flag.
In the ScalaTest Maven Plugin, set parallel to true.
In sbt, parallel execution is the default, but to be explicit you can write:
parallelExecution in Test := true // the default in sbt
On the JVM, if both ParallelTestExecution is mixed in and
parallel execution is enabled in the build, tests in an async-style suite will be started in parallel, using threads from
the Distributor, and allowed to complete in parallel, using threads from the
executionContext. If you are using ScalaTest's serial execution context, the JVM default, asynchronous tests will
run in parallel very much like traditional (such as AnyFreeSpec) tests run in
parallel: 1) Because ParallelTestExecution extends
OneInstancePerTest, each test will run in its own instance of the test class, you need not worry about synchronizing
access to mutable instance state shared by different tests in the same suite.
2) Because the serial execution context will confine the execution of each test to the single thread that executes the test body,
you need not worry about synchronizing access to shared mutable state accessed by transformations and callbacks of Futures
inside the test.
If ParallelTestExecution is mixed in but
parallel execution of suites is not enabled, asynchronous tests on the JVM will be started sequentially, by the single thread
that invoked run, but without waiting for one test to complete before the next test is started. As a result,
asynchronous tests will be allowed to complete in parallel, using threads
from the executionContext. If you are using the serial execution context, however, you'll see
the same behavior you see when parallel execution is disabled and a traditional suite that mixes in ParallelTestExecution
is executed: the tests will run sequentially. If you use an execution context backed by a thread-pool, such as global,
however, even though tests will be started sequentially by one thread, they will be allowed to run concurrently using threads from the
execution context's thread pool.
The latter behavior is essentially what you'll see on Scala.js when you execute a suite that mixes in ParallelTestExecution.
Because only one thread exists when running under JavaScript, you can't "enable parallel execution of suites." However, it may
still be useful to run tests in parallel on Scala.js, because tests can invoke API calls that are truly asynchronous by calling into
external APIs that take advantage of non-JavaScript threads. Thus on Scala.js, ParallelTestExecution allows asynchronous
tests to run in parallel, even though they must be started sequentially. This may give you better performance when you are using API
calls in your Scala.js tests that are truly asynchronous.
If you need to test for expected exceptions in the context of futures, you can use the
recoverToSucceededIf and recoverToExceptionIf methods of trait
RecoverMethods. Because this trait is mixed into
supertrait AsyncTestSuite, both of these methods are
available by default in an AsyncFreeSpec.
If you just want to ensure that a future fails with a particular exception type, and do
not need to inspect the exception further, use recoverToSucceededIf:
recoverToSucceededIf[IllegalStateException] { // Result type: Future[Assertion]
emptyStackActor ? Peek
}
The recoverToSucceededIf method performs a job similar to
assertThrows, except
in the context of a future. It transforms a Future of any type into a
Future[Assertion] that succeeds only if the original future fails with the specified
exception. Here's an example in the REPL:
scala> import org.scalatest.RecoverMethods._
import org.scalatest.RecoverMethods._
scala> import scala.concurrent.Future
import scala.concurrent.Future
scala> import scala.concurrent.ExecutionContext.Implicits.global
import scala.concurrent.ExecutionContext.Implicits.global
scala> recoverToSucceededIf[IllegalStateException] {
| Future { throw new IllegalStateException }
| }
res0: scala.concurrent.Future[org.scalatest.Assertion] = ...
scala> res0.value
res1: Option[scala.util.Try[org.scalatest.Assertion]] = Some(Success(Succeeded))
Otherwise it fails with an error message similar to those given by assertThrows:
scala> recoverToSucceededIf[IllegalStateException] {
| Future { throw new RuntimeException }
| }
res2: scala.concurrent.Future[org.scalatest.Assertion] = ...
scala> res2.value
res3: Option[scala.util.Try[org.scalatest.Assertion]] =
Some(Failure(org.scalatest.exceptions.TestFailedException: Expected exception
java.lang.IllegalStateException to be thrown, but java.lang.RuntimeException
was thrown))
scala> recoverToSucceededIf[IllegalStateException] {
| Future { 42 }
| }
res4: scala.concurrent.Future[org.scalatest.Assertion] = ...
scala> res4.value
res5: Option[scala.util.Try[org.scalatest.Assertion]] =
Some(Failure(org.scalatest.exceptions.TestFailedException: Expected exception
java.lang.IllegalStateException to be thrown, but no exception was thrown))
The recoverToExceptionIf method differs from the recoverToSucceededIf in
its behavior when the assertion succeeds: recoverToSucceededIf yields a Future[Assertion],
whereas recoverToExceptionIf yields a Future[T], where T is the
expected exception type.
recoverToExceptionIf[IllegalStateException] { // Result type: Future[IllegalStateException]
emptyStackActor ? Peek
}
In other words, recoverToExpectionIf is to
intercept as
recovertToSucceededIf is to assertThrows. The first one allows you to
perform further assertions on the expected exception. The second one gives you a result type that will satisfy the type checker
at the end of the test body. Here's an example showing recoverToExceptionIf in the REPL:
scala> val futureEx =
| recoverToExceptionIf[IllegalStateException] {
| Future { throw new IllegalStateException("hello") }
| }
futureEx: scala.concurrent.Future[IllegalStateException] = ...
scala> futureEx.value
res6: Option[scala.util.Try[IllegalStateException]] =
Some(Success(java.lang.IllegalStateException: hello))
scala> futureEx map { ex => assert(ex.getMessage == "world") }
res7: scala.concurrent.Future[org.scalatest.Assertion] = ...
scala> res7.value
res8: Option[scala.util.Try[org.scalatest.Assertion]] =
Some(Failure(org.scalatest.exceptions.TestFailedException: "[hello]" did not equal "[world]"))
To support the common use case of temporarily disabling a test, with the
good intention of resurrecting the test at a later time, AsyncFreeSpec adds a method
ignore to strings that can be used instead of in to register a test. For example, to temporarily
disable the test with the name "addSoon will eventually compute a sum of passed Ints", just
change “in” into “ignore,” like this:
package org.scalatest.examples.asyncfreespec.ignore
import org.scalatest.freespec.AsyncFreeSpec
import scala.concurrent.Future
class AddSpec extends AsyncFreeSpec {
def addSoon(addends: Int*): Future[Int] = Future { addends.sum }
"addSoon" - {
"will eventually compute a sum of passed Ints" ignore {
val futureSum: Future[Int] = addSoon(1, 2)
// You can map assertions onto a Future, then return
// the resulting Future[Assertion] to ScalaTest:
futureSum map { sum => assert(sum == 3) }
}
}
def addNow(addends: Int*): Int = addends.sum
"addNow" - {
"will immediately compute a sum of passed Ints" in {
val sum: Int = addNow(1, 2)
// You can also write synchronous tests. The body
// must have result type Assertion:
assert(sum == 3)
}
}
}
If you run this version of AddSpec with:
scala> org.scalatest.run(new AddSpec)
It will run only the second test and report that the first test was ignored:
AddSpec: addSoon - will eventually compute a sum of passed Ints !!! IGNORED !!! addNow - will immediately compute a sum of passed Ints
If you wish to temporarily ignore an entire suite of tests, you can (on the JVM, not Scala.js) annotate the test class with @Ignore, like this:
package org.scalatest.examples.asyncfreespec.ignoreall
import org.scalatest.freespec.AsyncFreeSpec
import scala.concurrent.Future
import org.scalatest.Ignore
@Ignore
class AddSpec extends AsyncFreeSpec {
def addSoon(addends: Int*): Future[Int] = Future { addends.sum }
"addSoon" - {
"will eventually compute a sum of passed Ints" in {
val futureSum: Future[Int] = addSoon(1, 2)
// You can map assertions onto a Future, then return
// the resulting Future[Assertion] to ScalaTest:
futureSum map { sum => assert(sum == 3) }
}
}
def addNow(addends: Int*): Int = addends.sum
"addNow" - {
"will immediately compute a sum of passed Ints" in {
val sum: Int = addNow(1, 2)
// You can also write synchronous tests. The body
// must have result type Assertion:
assert(sum == 3)
}
}
}
When you mark a test class with a tag annotation, ScalaTest will mark each test defined in that class with that tag.
Thus, marking the AddSpec in the above example with the @Ignore tag annotation means that both tests
in the class will be ignored. If you run the above AddSpec in the Scala interpreter, you'll see:
AddSpec: addSoon - will eventually compute a sum of passed Ints !!! IGNORED !!! addNow - will immediately compute a sum of passed Ints !!! IGNORED !!!
Note that marking a test class as ignored won't prevent it from being discovered by ScalaTest. Ignored classes
will be discovered and run, and all their tests will be reported as ignored. This is intended to keep the ignored
class visible, to encourage the developers to eventually fix and “un-ignore” it. If you want to
prevent a class from being discovered at all (on the JVM, not Scala.js), use the DoNotDiscover
annotation instead.
If you want to ignore all tests of a suite on Scala.js, where annotations can't be inspected at runtime, you'll need
to change it to ignore at each test site. To make a suite non-discoverable on Scala.js, ensure it
does not declare a public no-arg constructor. You can either declare a public constructor that takes one or more
arguments, or make the no-arg constructor non-public. Because this technique will also make the suite non-discoverable
on the JVM, it is a good approach for suites you want to run (but not be discoverable) on both Scala.js and the JVM.
One of the parameters to AsyncFreeSpec's run method is a Reporter, which
will collect and report information about the running suite of tests.
Information about suites and tests that were run, whether tests succeeded or failed,
and tests that were ignored will be passed to the Reporter as the suite runs.
Most often the reporting done by default by AsyncFreeSpec's methods will be sufficient, but
occasionally you may wish to provide custom information to the Reporter from a test.
For this purpose, an Informer that will forward information to the current Reporter
is provided via the info parameterless method.
You can pass the extra information to the Informer via its apply method.
The Informer will then pass the information to the Reporter via an InfoProvided event.
One use case for the Informer is to pass more information about a specification to the reporter. For example,
the GivenWhenThen trait provides methods that use the implicit info provided by AsyncFreeSpec
to pass such information to the reporter. Here's an example:
package org.scalatest.examples.asyncfreespec.info
import collection.mutable
import org.scalatest._
class SetSpec extends freespec.AsyncFreeSpec with GivenWhenThen {
"A mutable Set" - {
"should allow an element to be added" in {
Given("an empty mutable Set")
val set = mutable.Set.empty[String]
When("an element is added")
set += "clarity"
Then("the Set should have size 1")
assert(set.size === 1)
And("the Set should contain the added element")
assert(set.contains("clarity"))
info("That's all folks!")
succeed
}
}
}
If you run this AsyncFreeSpec from the interpreter, you will see the following output:
scala> org.scalatest.run(new SetSpec)
A mutable Set
- should allow an element to be added
+ Given an empty mutable Set
+ When an element is added
+ Then the Set should have size 1
+ And the Set should contain the added element
+ That's all folks!
AsyncFreeSpec also provides a markup method that returns a Documenter, which allows you to send
to the Reporter text formatted in Markdown syntax.
You can pass the extra information to the Documenter via its apply method.
The Documenter will then pass the information to the Reporter via an MarkupProvided event.
Here's an example AsyncFreeSpec that uses markup:
package org.scalatest.examples.asyncfreespec.markup
import collection.mutable
import org.scalatest._
class SetSpec extends freespec.AsyncFreeSpec with GivenWhenThen {
markup { """
Mutable Set
-----------
A set is a collection that contains no duplicate elements.
To implement a concrete mutable set, you need to provide implementations
of the following methods:
def contains(elem: A): Boolean
def iterator: Iterator[A]
def += (elem: A): this.type
def -= (elem: A): this.type
If you wish that methods like `take`,
`drop`, `filter` return the same kind of set,
you should also override:
def empty: This
It is also good idea to override methods `foreach` and
`size` for efficiency.
""" }
"A mutable Set" - {
"should allow an element to be added" in {
Given("an empty mutable Set")
val set = mutable.Set.empty[String]
When("an element is added")
set += "clarity"
Then("the Set should have size 1")
assert(set.size === 1)
And("the Set should contain the added element")
assert(set.contains("clarity"))
markup("This test finished with a **bold** statement!")
succeed
}
}
}
Although all of ScalaTest's built-in reporters will display the markup text in some form,
the HTML reporter will format the markup information into HTML. Thus, the main purpose of markup is to
add nicely formatted text to HTML reports. Here's what the above SetSpec would look like in the HTML reporter:
ScalaTest records text passed to info and markup during tests, and sends the recorded text in the recordedEvents field of
test completion events like TestSucceeded and TestFailed. This allows string reporters (like the standard out reporter) to show
info and markup text after the test name in a color determined by the outcome of the test. For example, if the test fails, string
reporters will show the info and markup text in red. If a test succeeds, string reporters will show the info
and markup text in green. While this approach helps the readability of reports, it means that you can't use info to get status
updates from long running tests.
To get immediate (i.e., non-recorded) notifications from tests, you can use note (a Notifier) and alert
(an Alerter). Here's an example showing the differences:
package org.scalatest.examples.asyncfreespec.note
import collection.mutable
import org.scalatest._
class SetSpec extends freespec.AsyncFreeSpec {
"A mutable Set" - {
"should allow an element to be added" in {
info("info is recorded")
markup("markup is *also* recorded")
note("notes are sent immediately")
alert("alerts are also sent immediately")
val set = mutable.Set.empty[String]
set += "clarity"
assert(set.size === 1)
assert(set.contains("clarity"))
}
}
}
scala> org.scalatest.run(new SetSpec) SetSpec: A mutable Set + notes are sent immediately + alerts are also sent immediately - should allow an element to be added + info is recorded + markup is *also* recorded
Another example is slowpoke notifications.
If you find a test is taking a long time to complete, but you're not sure which test, you can enable
slowpoke notifications. ScalaTest will use an Alerter to fire an event whenever a test has been running
longer than a specified amount of time.
In summary, use info and markup for text that should form part of the specification output. Use
note and alert to send status notifications. (Because the HTML reporter is intended to produce a
readable, printable specification, info and markup text will appear in the HTML report, but
note and alert text will not.)
A pending test is one that has been given a name but is not yet implemented. The purpose of pending tests is to facilitate a style of testing in which documentation of behavior is sketched out before tests are written to verify that behavior (and often, before the behavior of the system being tested is itself implemented). Such sketches form a kind of specification of what tests and functionality to implement later.
To support this style of testing, a test can be given a name that specifies one
bit of behavior required by the system being tested. At the end of the test,
it can call method pending, which will cause it to complete abruptly with TestPendingException.
Because tests in ScalaTest can be designated as pending with TestPendingException, both the test name and any information
sent to the reporter when running the test can appear in the report of a test run. (In other words,
the code of a pending test is executed just like any other test.) However, because the test completes abruptly
with TestPendingException, the test will be reported as pending, to indicate
the actual test, and possibly the functionality, has not yet been implemented. Here's an example:
package org.scalatest.examples.asyncfreespec.pending
import org.scalatest.freespec.AsyncFreeSpec
import scala.concurrent.Future
class AddSpec extends AsyncFreeSpec {
def addSoon(addends: Int*): Future[Int] = Future { addends.sum }
"addSoon" - {
"will eventually compute a sum of passed Ints" in (pending)
}
def addNow(addends: Int*): Int = addends.sum
"addNow" - {
"will immediately compute a sum of passed Ints" in {
val sum: Int = addNow(1, 2)
// You can also write synchronous tests. The body
// must have result type Assertion:
assert(sum == 3)
}
}
}
(Note: "(pending)" is the body of the test. Thus the test contains just one statement, an invocation
of the pending method, which throws TestPendingException.)
If you run this version of AddSpec with:
scala> org.scalatest.run(new AddSpec)
It will run both tests, but report that first test is pending. You'll see:
AddSpec: addSoon - will eventually compute a sum of passed Ints (pending) addNow - will immediately compute a sum of passed Ints
One difference between an ignored test and a pending one is that an ignored test is intended to be used during significant refactorings of the code under test, when tests break and you don't want to spend the time to fix all of them immediately. You can mark some of those broken tests as ignored temporarily, so that you can focus the red bar on just failing tests you actually want to fix immediately. Later you can go back and fix the ignored tests. In other words, by ignoring some failing tests temporarily, you can more easily notice failed tests that you actually want to fix. By contrast, a pending test is intended to be used before a test and/or the code under test is written. Pending indicates you've decided to write a test for a bit of behavior, but either you haven't written the test yet, or have only written part of it, or perhaps you've written the test but don't want to implement the behavior it tests until after you've implemented a different bit of behavior you realized you need first. Thus ignored tests are designed to facilitate refactoring of existing code whereas pending tests are designed to facilitate the creation of new code.
One other difference between ignored and pending tests is that ignored tests are implemented as a test tag that is
excluded by default. Thus an ignored test is never executed. By contrast, a pending test is implemented as a
test that throws TestPendingException (which is what calling the pending method does). Thus
the body of pending tests are executed up until they throw TestPendingException.
An AsyncFreeSpec's tests may be classified into groups by tagging them with string names.
As with any suite, when executing an AsyncFreeSpec, groups of tests can
optionally be included and/or excluded. To tag an AsyncFreeSpec's tests,
you pass objects that extend class org.scalatest.Tag to methods
that register tests. Class Tag takes one parameter, a string name. If you have
created tag annotation interfaces as described in the Tag documentation, then you
will probably want to use tag names on your test functions that match. To do so, simply
pass the fully qualified names of the tag interfaces to the Tag constructor. For example, if you've
defined a tag annotation interface with fully qualified name,
com.mycompany.tags.DbTest, then you could
create a matching tag for AsyncFreeSpecs like this:
package org.scalatest.examples.asyncfreespec.tagging
import org.scalatest.Tag
object DbTest extends Tag("com.mycompany.tags.DbTest")
Given these definitions, you could place AsyncFreeSpec tests into groups with tags like this:
import org.scalatest.freespec.AsyncFreeSpec
import org.scalatest.tagobjects.Slow
import scala.concurrent.Future
class AddSpec extends AsyncFreeSpec {
def addSoon(addends: Int*): Future[Int] = Future { addends.sum }
"addSoon" - {
"will eventually compute a sum of passed Ints" taggedAs(Slow) in {
val futureSum: Future[Int] = addSoon(1, 2)
// You can map assertions onto a Future, then return
// the resulting Future[Assertion] to ScalaTest:
futureSum map { sum => assert(sum == 3) }
}
}
def addNow(addends: Int*): Int = addends.sum
"addNow" - {
"will immediately compute a sum of passed Ints" taggedAs(Slow, DbTest) in {
val sum: Int = addNow(1, 2)
// You can also write synchronous tests. The body
// must have result type Assertion:
assert(sum == 3)
}
}
}
This code marks both tests with the org.scalatest.tags.Slow tag,
and the second test with the com.mycompany.tags.DbTest tag.
The run method takes a Filter, whose constructor takes an optional
Set[String] called tagsToInclude and a Set[String] called
tagsToExclude. If tagsToInclude is None, all tests will be run
except those those belonging to tags listed in the
tagsToExclude Set. If tagsToInclude is defined, only tests
belonging to tags mentioned in the tagsToInclude set, and not mentioned in tagsToExclude,
will be run.
It is recommended, though not required, that you create a corresponding tag annotation when you
create a Tag object. A tag annotation (on the JVM, not Scala.js) allows you to tag all the tests of an AsyncFreeSpec in
one stroke by annotating the class. For more information and examples, see the
documentation for class Tag. On Scala.js, to tag all tests of a suite, you'll need to
tag each test individually at the test site.
A test fixture is composed of the objects and other artifacts (files, sockets, database connections, etc.) tests use to do their work. When multiple tests need to work with the same fixtures, it is important to try and avoid duplicating the fixture code across those tests. The more code duplication you have in your tests, the greater drag the tests will have on refactoring the actual production code.
ScalaTest recommends three techniques to eliminate such code duplication in async styles:
withFixtureEach technique is geared towards helping you reduce code duplication without introducing
instance vars, shared mutable objects, or other dependencies between tests. Eliminating shared
mutable state across tests will make your test code easier to reason about and eliminate the need to
synchronize access to shared mutable state on the JVM.
The following sections describe these techniques, including explaining the recommended usage for each. But first, here's a table summarizing the options:
| Refactor using Scala when different tests need different fixtures. | |
| get-fixture methods | The extract method refactor helps you create a fresh instances of mutable fixture objects in each test that needs them, but doesn't help you clean them up when you're done. |
| loan-fixture methods | Factor out dupicate code with the loan pattern when different tests need different fixtures that must be cleaned up afterwards. |
Override withFixture when most or all tests need the same fixture.
|
|
withFixture(NoArgAsyncTest)
|
The recommended default approach when most or all tests need the same fixture treatment. This general technique
allows you, for example, to perform side effects at the beginning and end of all or most tests,
transform the outcome of tests, retry tests, make decisions based on test names, tags, or other test data.
Use this technique unless:
|
withFixture(OneArgAsyncTest)
|
Use when you want to pass the same fixture object or objects as a parameter into all or most tests. |
| Mix in a before-and-after trait when you want an aborted suite, not a failed test, if the fixture code fails. | |
BeforeAndAfter
|
Use this boilerplate-buster when you need to perform the same side-effects before and/or after tests, rather than at the beginning or end of tests. |
BeforeAndAfterEach
|
Use when you want to stack traits that perform the same side-effects before and/or after tests, rather than at the beginning or end of tests. |
If you need to create the same mutable fixture objects in multiple tests, and don't need to clean them up after using them, the simplest approach is to write one or more get-fixture methods. A get-fixture method returns a new instance of a needed fixture object (or a holder object containing multiple fixture objects) each time it is called. You can call a get-fixture method at the beginning of each test that needs the fixture, storing the returned object or objects in local variables. Here's an example:
package org.scalatest.examples.asyncfreespec.getfixture
import org.scalatest.freespec.AsyncFreeSpec
import scala.concurrent.Future
class ExampleSpec extends AsyncFreeSpec {
def fixture: Future[String] = Future { "ScalaTest is " }
"Testing" - {
"should be easy" in {
val future = fixture
val result = future map { s => s + "easy!" }
result map { s =>
assert(s == "ScalaTest is easy!")
}
}
"should be fun" in {
val future = fixture
val result = future map { s => s + "fun!" }
result map { s =>
assert(s == "ScalaTest is fun!")
}
}
}
}
If you need to configure fixture objects differently in different tests, you can pass configuration into the get-fixture method. For example, you could pass in an initial value for a fixture object as a parameter to the get-fixture method.
withFixture(NoArgAsyncTest) Although the get-fixture method approach takes care of setting up a fixture at the beginning of each
test, it doesn't address the problem of cleaning up a fixture at the end of the test. If you just need to perform a side-effect at the beginning or end of
a test, and don't need to actually pass any fixture objects into the test, you can override withFixture(NoArgAsyncTest), a
method defined in trait AsyncTestSuite, a supertrait of AsyncFreeSpec.
Trait AsyncFreeSpec's runTest method passes a no-arg async test function to
withFixture(NoArgAsyncTest). It is withFixture's
responsibility to invoke that test function. The default implementation of withFixture simply
invokes the function and returns the result, like this:
// Default implementation in trait AsyncTestSuite
protected def withFixture(test: NoArgAsyncTest): FutureOutcome = {
test()
}
You can, therefore, override withFixture to perform setup before invoking the test function,
and/or perform cleanup after the test completes. The recommended way to ensure cleanup is performed after a test completes is
to use the complete-lastly syntax, defined in supertrait CompleteLastly.
The complete-lastly syntax will ensure that
cleanup will occur whether future-producing code completes abruptly by throwing an exception, or returns
normally yielding a future. In the latter case, complete-lastly will register the cleanup code
to execute asynchronously when the future completes.
The withFixture method is designed to be stacked, and to enable this, you should always call the super implementation
of withFixture, and let it invoke the test function rather than invoking the test function directly. In other words, instead of writing
“test()”, you should write “super.withFixture(test)”, like this:
// Your implementation
override def withFixture(test: NoArgAsyncTest) = {
// Perform setup here
complete {
super.withFixture(test) // Invoke the test function
} lastly {
// Perform cleanup here
}
}
If you have no cleanup to perform, you can write withFixture like this instead:
// Your implementation
override def withFixture(test: NoArgAsyncTest) = {
// Perform setup here
super.withFixture(test) // Invoke the test function
}
If you want to perform an action only for certain outcomes, you'll need to
register code performing that action as a callback on the Future using
one of Future's registration methods: onComplete, onSuccess,
or onFailure. Note that if a test fails, that will be treated as a
scala.util.Success(org.scalatest.Failed). So if you want to perform an
action if a test fails, for example, you'd register the callback using onSuccess.
Here's an example in which withFixture(NoArgAsyncTest) is used to take a
snapshot of the working directory if a test fails, and
send that information to the standard output stream:
package org.scalatest.examples.asyncfreespec.noargasynctest
import java.io.File
import org.scalatest._
import scala.concurrent.Future
class ExampleSpec extends freespec.AsyncFreeSpec {
override def withFixture(test: NoArgAsyncTest) = {
super.withFixture(test) onFailedThen { _ =>
val currDir = new File(".")
val fileNames = currDir.list()
info("Dir snapshot: " + fileNames.mkString(", "))
}
}
def addSoon(addends: Int*): Future[Int] = Future { addends.sum }
"This test" - {
"should succeed" in {
addSoon(1, 1) map { sum => assert(sum == 2) }
}
"should fail" in {
addSoon(1, 1) map { sum => assert(sum == 3) }
}
}
}
Running this version of ExampleSpec in the interpreter in a directory with two files, hello.txt and world.txt
would give the following output:
scala> org.scalatest.run(new ExampleSpec) ExampleSpec: This test - should succeed - should fail *** FAILED *** 2 did not equal 3 (:33)
Note that the NoArgAsyncTest passed to withFixture, in addition to
an apply method that executes the test, also includes the test name and the config
map passed to runTest. Thus you can also use the test name and configuration objects in your withFixture
implementation.
Lastly, if you want to transform the outcome in some way in withFixture, you'll need to use either the
map or transform methods of Future, like this:
// Your implementation
override def withFixture(test: NoArgAsyncTest) = {
// Perform setup here
val futureOutcome = super.withFixture(test) // Invoke the test function
futureOutcome change { outcome =>
// transform the outcome into a new outcome here
}
}
Note that a NoArgAsyncTest's apply method will return a scala.util.Failure only if
the test completes abruptly with a "test-fatal" exception (such as OutOfMemoryError) that should
cause the suite to abort rather than the test to fail. Thus usually you would use map
to transform future outcomes, not transform, so that such test-fatal exceptions pass through
unchanged. The suite will abort asynchronously with any exception returned from NoArgAsyncTest's
apply method in a scala.util.Failure.
If you need to both pass a fixture object into a test and perform cleanup at the end of the test, you'll need to use the loan pattern. If different tests need different fixtures that require cleanup, you can implement the loan pattern directly by writing loan-fixture methods. A loan-fixture method takes a function whose body forms part or all of a test's code. It creates a fixture, passes it to the test code by invoking the function, then cleans up the fixture after the function returns.
The following example shows three tests that use two fixtures, a database and a file. Both require cleanup after, so each is provided via a
loan-fixture method. (In this example, the database is simulated with a StringBuffer.)
package org.scalatest.examples.asyncfreespec.loanfixture
import java.util.concurrent.ConcurrentHashMap
import scala.concurrent.Future
import scala.concurrent.ExecutionContext
object DbServer { // Simulating a database server
type Db = StringBuffer
private final val databases = new ConcurrentHashMap[String, Db]
def createDb(name: String): Db = {
val db = new StringBuffer // java.lang.StringBuffer is thread-safe
databases.put(name, db)
db
}
def removeDb(name: String): Unit = {
databases.remove(name)
}
}
// Defining actor messages
sealed abstract class StringOp
case object Clear extends StringOp
case class Append(value: String) extends StringOp
case object GetValue
class StringActor { // Simulating an actor
private final val sb = new StringBuilder
def !(op: StringOp): Unit =
synchronized {
op match {
case Append(value) => sb.append(value)
case Clear => sb.clear()
}
}
def ?(get: GetValue.type)(implicit c: ExecutionContext): Future[String] =
Future {
synchronized { sb.toString }
}
}
import org.scalatest._
import DbServer._
import java.util.UUID.randomUUID
class ExampleSpec extends freespec.AsyncFreeSpec {
def withDatabase(testCode: Future[Db] => Future[Assertion]) = {
val dbName = randomUUID.toString // generate a unique db name
val futureDb = Future { createDb(dbName) } // create the fixture
complete {
val futurePopulatedDb =
futureDb map { db =>
db.append("ScalaTest is ") // perform setup
}
testCode(futurePopulatedDb) // "loan" the fixture to the test code
} lastly {
removeDb(dbName) // ensure the fixture will be cleaned up
}
}
def withActor(testCode: StringActor => Future[Assertion]) = {
val actor = new StringActor
complete {
actor ! Append("ScalaTest is ") // set up the fixture
testCode(actor) // "loan" the fixture to the test code
} lastly {
actor ! Clear // ensure the fixture will be cleaned up
}
}
"Testing" - {
// This test needs the actor fixture
"should be productive" in {
withActor { actor =>
actor ! Append("productive!")
val futureString = actor ? GetValue
futureString map { s =>
assert(s == "ScalaTest is productive!")
}
}
}
}
"Test code" - {
// This test needs the database fixture
"should be readable" in {
withDatabase { futureDb =>
futureDb map { db =>
db.append("readable!")
assert(db.toString == "ScalaTest is readable!")
}
}
}
// This test needs both the actor and the database
"should be clear and concise" in {
withDatabase { futureDb =>
withActor { actor => // loan-fixture methods compose
actor ! Append("concise!")
val futureString = actor ? GetValue
val futurePair: Future[(Db, String)] =
futureDb zip futureString
futurePair map { case (db, s) =>
db.append("clear!")
assert(db.toString == "ScalaTest is clear!")
assert(s == "ScalaTest is concise!")
}
}
}
}
}
}
As demonstrated by the last test, loan-fixture methods compose. Not only do loan-fixture methods allow you to give each test the fixture it needs, they allow you to give a test multiple fixtures and clean everything up afterwards.
Also demonstrated in this example is the technique of giving each test its own "fixture sandbox" to play in. When your fixtures involve external side-effects, like creating databases, it is a good idea to give each database a unique name as is done in this example. This keeps tests completely isolated, allowing you to run them in parallel if desired.
withFixture(OneArgTest) If all or most tests need the same fixture, you can avoid some of the boilerplate of the loan-fixture method approach by using a
fixture.AsyncTestSuite and overriding withFixture(OneArgAsyncTest).
Each test in a fixture.AsyncTestSuite takes a fixture as a parameter, allowing you to pass the fixture into
the test. You must indicate the type of the fixture parameter by specifying FixtureParam, and implement a
withFixture method that takes a OneArgAsyncTest. This withFixture method is responsible for
invoking the one-arg async test function, so you can perform fixture set up before invoking and passing
the fixture into the test function, and ensure clean up is performed after the test completes.
To enable the stacking of traits that define withFixture(NoArgAsyncTest), it is a good idea to let
withFixture(NoArgAsyncTest) invoke the test function instead of invoking the test
function directly. To do so, you'll need to convert the OneArgAsyncTest to a NoArgAsyncTest. You can do that by passing
the fixture object to the toNoArgAsyncTest method of OneArgAsyncTest. In other words, instead of
writing “test(theFixture)”, you'd delegate responsibility for
invoking the test function to the withFixture(NoArgAsyncTest) method of the same instance by writing:
withFixture(test.toNoArgAsyncTest(theFixture))
Here's a complete example:
package org.scalatest.examples.asyncfreespec.oneargasynctest
import org.scalatest._
import scala.concurrent.Future
import scala.concurrent.ExecutionContext
// Defining actor messages
sealed abstract class StringOp
case object Clear extends StringOp
case class Append(value: String) extends StringOp
case object GetValue
class StringActor { // Simulating an actor
private final val sb = new StringBuilder
def !(op: StringOp): Unit =
synchronized {
op match {
case Append(value) => sb.append(value)
case Clear => sb.clear()
}
}
def ?(get: GetValue.type)(implicit c: ExecutionContext): Future[String] =
Future {
synchronized { sb.toString }
}
}
class ExampleSpec extends freespec.FixtureAsyncFreeSpec {
type FixtureParam = StringActor
def withFixture(test: OneArgAsyncTest): FutureOutcome = {
val actor = new StringActor
complete {
actor ! Append("ScalaTest is ") // set up the fixture
withFixture(test.toNoArgAsyncTest(actor))
} lastly {
actor ! Clear // ensure the fixture will be cleaned up
}
}
"Testing" - {
"should be easy" in { actor =>
actor ! Append("easy!")
val futureString = actor ? GetValue
futureString map { s =>
assert(s == "ScalaTest is easy!")
}
}
"should be fun" in { actor =>
actor ! Append("fun!")
val futureString = actor ? GetValue
futureString map { s =>
assert(s == "ScalaTest is fun!")
}
}
}
}
In this example, the tests required one fixture object, a StringActor. If your tests need multiple fixture objects, you can
simply define the FixtureParam type to be a tuple containing the objects or, alternatively, a case class containing
the objects. For more information on the withFixture(OneArgAsyncTest) technique, see
the documentation for FixtureAsyncFreeSpec.
BeforeAndAfter In all the shared fixture examples shown so far, the activities of creating, setting up, and cleaning up the fixture objects have been
performed during the test. This means that if an exception occurs during any of these activities, it will be reported as a test failure.
Sometimes, however, you may want setup to happen before the test starts, and cleanup after the test has completed, so that if an
exception occurs during setup or cleanup, the entire suite aborts and no more tests are attempted. The simplest way to accomplish this in ScalaTest is
to mix in trait BeforeAndAfter. With this trait you can denote a bit of code to run before each test
with before and/or after each test each test with after, like this:
package org.scalatest.examples.asyncfreespec.beforeandafter
import org.scalatest.freespec.AsyncFreeSpec
import org.scalatest.BeforeAndAfter
import scala.concurrent.Future
import scala.concurrent.ExecutionContext
// Defining actor messages
sealed abstract class StringOp
case object Clear extends StringOp
case class Append(value: String) extends StringOp
case object GetValue
class StringActor { // Simulating an actor
private final val sb = new StringBuilder
def !(op: StringOp): Unit =
synchronized {
op match {
case Append(value) => sb.append(value)
case Clear => sb.clear()
}
}
def ?(get: GetValue.type)(implicit c: ExecutionContext): Future[String] =
Future {
synchronized { sb.toString }
}
}
class ExampleSpec extends AsyncFreeSpec with BeforeAndAfter {
final val actor = new StringActor
before {
actor ! Append("ScalaTest is ") // set up the fixture
}
after {
actor ! Clear // clean up the fixture
}
"Testing" - {
"should be easy" in {
actor ! Append("easy!")
val futureString = actor ? GetValue
futureString map { s =>
assert(s == "ScalaTest is easy!")
}
}
"should be fun" in {
actor ! Append("fun!")
val futureString = actor ? GetValue
futureString map { s =>
assert(s == "ScalaTest is fun!")
}
}
}
}
Note that the only way before and after code can communicate with test code is via some
side-effecting mechanism, commonly by reassigning instance vars or by changing the state of mutable
objects held from instance vals (as in this example). If using instance vars or
mutable objects held from instance vals you wouldn't be able to run tests in parallel in the same instance
of the test class (on the JVM, not Scala.js) unless you synchronized access to the shared, mutable state.
Note that on the JVM, if you override ScalaTest's default
serial execution context, you will likely need to
worry about synchronizing access to shared mutable fixture state, because the execution
context may assign different threads to process
different Future transformations. Although access to mutable state along
the same linear chain of Future transformations need not be synchronized,
it can be difficult to spot cases where these constraints are violated. The best approach
is to use only immutable objects when transforming Futures. When that's not
practical, involve only thread-safe mutable objects, as is done in the above example.
On Scala.js, by contrast, you need not worry about thread synchronization, because
in effect only one thread exists.
Although BeforeAndAfter provides a minimal-boilerplate way to execute code before and after tests, it isn't designed to enable stackable
traits, because the order of execution would be non-obvious. If you want to factor out before and after code that is common to multiple test suites, you
should use trait BeforeAndAfterEach instead, as shown later in the next section,
composing fixtures by stacking traits.
In larger projects, teams often end up with several different fixtures that test classes need in different combinations,
and possibly initialized (and cleaned up) in different orders. A good way to accomplish this in ScalaTest is to factor the individual
fixtures into traits that can be composed using the stackable trait pattern. This can be done, for example, by placing
withFixture methods in several traits, each of which call super.withFixture. Here's an example in
which the StringBuilderActor and StringBufferActor fixtures used in the previous examples have been
factored out into two stackable fixture traits named Builder and Buffer:
package org.scalatest.examples.asyncfreespec.composingwithasyncfixture
import org.scalatest._
import org.scalatest.SuiteMixin
import collection.mutable.ListBuffer
import scala.concurrent.Future
import scala.concurrent.ExecutionContext
// Defining actor messages
sealed abstract class StringOp
case object Clear extends StringOp
case class Append(value: String) extends StringOp
case object GetValue
class StringBuilderActor { // Simulating an actor
private final val sb = new StringBuilder
def !(op: StringOp): Unit =
synchronized {
op match {
case Append(value) => sb.append(value)
case Clear => sb.clear()
}
}
def ?(get: GetValue.type)(implicit c: ExecutionContext): Future[String] =
Future {
synchronized { sb.toString }
}
}
class StringBufferActor {
private final val buf = ListBuffer.empty[String]
def !(op: StringOp): Unit =
synchronized {
op match {
case Append(value) => buf += value
case Clear => buf.clear()
}
}
def ?(get: GetValue.type)(implicit c: ExecutionContext): Future[List[String]] =
Future {
synchronized { buf.toList }
}
}
trait Builder extends AsyncTestSuiteMixin { this: AsyncTestSuite =>
final val builderActor = new StringBuilderActor
abstract override def withFixture(test: NoArgAsyncTest) = {
builderActor ! Append("ScalaTest is ")
complete {
super.withFixture(test) // To be stackable, must call super.withFixture
} lastly {
builderActor ! Clear
}
}
}
trait Buffer extends AsyncTestSuiteMixin { this: AsyncTestSuite =>
final val bufferActor = new StringBufferActor
abstract override def withFixture(test: NoArgAsyncTest) = {
complete {
super.withFixture(test) // To be stackable, must call super.withFixture
} lastly {
bufferActor ! Clear
}
}
}
class ExampleSpec extends freespec.AsyncFreeSpec with Builder with Buffer {
"Testing" - {
"should be easy" in {
builderActor ! Append("easy!")
val futureString = builderActor ? GetValue
val futureList = bufferActor ? GetValue
val futurePair: Future[(String, List[String])] = futureString zip futureList
futurePair map { case (str, lst) =>
assert(str == "ScalaTest is easy!")
assert(lst.isEmpty)
bufferActor ! Append("sweet")
succeed
}
}
"should be fun" in {
builderActor ! Append("fun!")
val futureString = builderActor ? GetValue
val futureList = bufferActor ? GetValue
val futurePair: Future[(String, List[String])] = futureString zip futureList
futurePair map { case (str, lst) =>
assert(str == "ScalaTest is fun!")
assert(lst.isEmpty)
bufferActor ! Append("awesome")
succeed
}
}
}
}
By mixing in both the Builder and Buffer traits, ExampleSpec gets both fixtures, which will be
initialized before each test and cleaned up after. The order the traits are mixed together determines the order of execution.
In this case, Builder is “super” to Buffer. If you wanted Buffer to be “super”
to Builder, you need only switch the order you mix them together, like this:
class Example2Spec extends freespec.AsyncFreeSpec with Buffer with Builder
If you only need one fixture you mix in only that trait:
class Example3Spec extends freespec.AsyncFreeSpec with Builder
Another way to create stackable fixture traits is by extending the BeforeAndAfterEach
and/or BeforeAndAfterAll traits.
BeforeAndAfterEach has a beforeEach method that will be run before each test (like JUnit's setUp),
and an afterEach method that will be run after (like JUnit's tearDown).
Similarly, BeforeAndAfterAll has a beforeAll method that will be run before all tests,
and an afterAll method that will be run after all tests. Here's what the previously shown example would look like if it
were rewritten to use the BeforeAndAfterEach methods instead of withFixture:
package org.scalatest.examples.asyncfreespec.composingbeforeandaftereach
import org.scalatest._
import org.scalatest.BeforeAndAfterEach
import collection.mutable.ListBuffer
import scala.concurrent.Future
import scala.concurrent.ExecutionContext
// Defining actor messages
sealed abstract class StringOp
case object Clear extends StringOp
case class Append(value: String) extends StringOp
case object GetValue
class StringBuilderActor { // Simulating an actor
private final val sb = new StringBuilder
def !(op: StringOp): Unit =
synchronized {
op match {
case Append(value) => sb.append(value)
case Clear => sb.clear()
}
}
def ?(get: GetValue.type)(implicit c: ExecutionContext): Future[String] =
Future {
synchronized { sb.toString }
}
}
class StringBufferActor {
private final val buf = ListBuffer.empty[String]
def !(op: StringOp): Unit =
synchronized {
op match {
case Append(value) => buf += value
case Clear => buf.clear()
}
}
def ?(get: GetValue.type)(implicit c: ExecutionContext): Future[List[String]] =
Future {
synchronized { buf.toList }
}
}
trait Builder extends BeforeAndAfterEach { this: Suite =>
final val builderActor = new StringBuilderActor
override def beforeEach() {
builderActor ! Append("ScalaTest is ")
super.beforeEach() // To be stackable, must call super.beforeEach
}
override def afterEach() {
try super.afterEach() // To be stackable, must call super.afterEach
finally builderActor ! Clear
}
}
trait Buffer extends BeforeAndAfterEach { this: Suite =>
final val bufferActor = new StringBufferActor
override def afterEach() {
try super.afterEach() // To be stackable, must call super.afterEach
finally bufferActor ! Clear
}
}
class ExampleSpec extends freespec.AsyncFreeSpec with Builder with Buffer {
"Testing" - {
"should be easy" in {
builderActor ! Append("easy!")
val futureString = builderActor ? GetValue
val futureList = bufferActor ? GetValue
val futurePair: Future[(String, List[String])] = futureString zip futureList
futurePair map { case (str, lst) =>
assert(str == "ScalaTest is easy!")
assert(lst.isEmpty)
bufferActor ! Append("sweet")
succeed
}
}
"should be fun" in {
builderActor ! Append("fun!")
val futureString = builderActor ? GetValue
val futureList = bufferActor ? GetValue
val futurePair: Future[(String, List[String])] = futureString zip futureList
futurePair map { case (str, lst) =>
assert(str == "ScalaTest is fun!")
assert(lst.isEmpty)
bufferActor ! Append("awesome")
succeed
}
}
}
}
To get the same ordering as withFixture, place your super.beforeEach call at the end of each
beforeEach method, and the super.afterEach call at the beginning of each afterEach
method, as shown in the previous example. It is a good idea to invoke super.afterEach in a try
block and perform cleanup in a finally clause, as shown in the previous example, because this ensures the
cleanup code is performed even if super.afterEach throws an exception.
The difference between stacking traits that extend BeforeAndAfterEach versus traits that implement withFixture is
that setup and cleanup code happens before and after the test in BeforeAndAfterEach, but at the beginning and
end of the test in withFixture. Thus if a withFixture method completes abruptly with an exception, it is
considered a failed test. By contrast, if any of the beforeEach or afterEach methods of BeforeAndAfterEach
complete abruptly, it is considered an aborted suite, which will result in a SuiteAborted event.
Sometimes you may want to run the same test code on different fixture objects. In other words, you may want to write tests that are "shared"
by different fixture objects.
To accomplish this in an AsyncFreeSpec, you first place shared tests in
behavior functions. These behavior functions will be
invoked during the construction phase of any AsyncFreeSpec that uses them, so that the tests they contain will
be registered as tests in that AsyncFreeSpec.
For example, given this StackActor class:
package org.scalatest.examples.asyncfreespec.sharedtests
import scala.collection.mutable.ListBuffer
import scala.concurrent.Future
import scala.concurrent.ExecutionContext
// Stack operations
case class Push[T](value: T)
sealed abstract class StackOp
case object Pop extends StackOp
case object Peek extends StackOp
case object Size extends StackOp
// Stack info
case class StackInfo[T](top: Option[T], size: Int, max: Int) {
require(size > 0, "size was less than zero")
require(max >= size, "max was less than size")
val isFull: Boolean = size == max
val isEmpty: Boolean = size == 0
}
class StackActor[T](Max: Int, name: String) {
private final val buf = new ListBuffer[T]
def !(push: Push[T]): Unit =
synchronized {
if (buf.size != Max)
buf.prepend(push.value)
else
throw new IllegalStateException("can't push onto a full stack")
}
def ?(op: StackOp)(implicit c: ExecutionContext): Future[StackInfo[T]] =
synchronized {
op match {
case Pop =>
Future {
if (buf.size != 0)
StackInfo(Some(buf.remove(0)), buf.size, Max)
else
throw new IllegalStateException("can't pop an empty stack")
}
case Peek =>
Future {
if (buf.size != 0)
StackInfo(Some(buf(0)), buf.size, Max)
else
throw new IllegalStateException("can't peek an empty stack")
}
case Size =>
Future { StackInfo(None, buf.size, Max) }
}
}
override def toString: String = name
}
You may want to test the stack represented by the StackActor class in different states: empty, full, with one item, with one item less than capacity,
etc. You may find you have several tests that make sense any time the stack is non-empty. Thus you'd ideally want to run
those same tests for three stack fixture objects: a full stack, a stack with a one item, and a stack with one item less than
capacity. With shared tests, you can factor these tests out into a behavior function, into which you pass the
stack fixture to use when running the tests. So in your AsyncFreeSpec for StackActor, you'd invoke the
behavior function three times, passing in each of the three stack fixtures so that the shared tests are run for all three fixtures.
You can define a behavior function that encapsulates these shared tests inside the AsyncFreeSpec that uses them. If they are shared
between different AsyncFreeSpecs, however, you could also define them in a separate trait that is mixed into
each AsyncFreeSpec that uses them.
For example, here the nonEmptyStackActor behavior function (in this case, a
behavior method) is defined in a trait along with another
method containing shared tests for non-full stacks:
import org.scalatest.freespec.AsyncFreeSpec
trait AsyncFreeSpecStackBehaviors { this: AsyncFreeSpec =>
def nonEmptyStackActor(createNonEmptyStackActor: => StackActor[Int],
lastItemAdded: Int, name: String): Unit = {
("return non-empty StackInfo when Size is fired at non-empty stack actor: " + name) in {
val stackActor = createNonEmptyStackActor
val futureStackInfo = stackActor ? Size
futureStackInfo map { stackInfo =>
assert(!stackInfo.isEmpty)
}
}
("return before and after StackInfo that has existing size and lastItemAdded as top when Peek is fired at non-empty stack actor: " + name) in {
val stackActor = createNonEmptyStackActor
val futurePair: Future[(StackInfo[Int], StackInfo[Int])] =
for {
beforePeek <- stackActor ? Size
afterPeek <- stackActor ? Peek
} yield (beforePeek, afterPeek)
futurePair map { case (beforePeek, afterPeek) =>
assert(afterPeek.top == Some(lastItemAdded))
assert(afterPeek.size == beforePeek.size)
}
}
("return before and after StackInfo that has existing size - 1 and lastItemAdded as top when Pop is fired at non-empty stack actor: " + name) in {
val stackActor = createNonEmptyStackActor
val futurePair: Future[(StackInfo[Int], StackInfo[Int])] =
for {
beforePop <- stackActor ? Size
afterPop <- stackActor ? Pop
} yield (beforePop, afterPop)
futurePair map { case (beforePop, afterPop) =>
assert(afterPop.top == Some(lastItemAdded))
assert(afterPop.size == beforePop.size - 1)
}
}
}
def nonFullStackActor(createNonFullStackActor: => StackActor[Int], name: String): Unit = {
("return non-full StackInfo when Size is fired at non-full stack actor: " + name) in {
val stackActor = createNonFullStackActor
val futureStackInfo = stackActor ? Size
futureStackInfo map { stackInfo =>
assert(!stackInfo.isFull)
}
}
("return before and after StackInfo that has existing size + 1 and new item as top when Push is fired at non-full stack actor: " + name) in {
val stackActor = createNonFullStackActor
val futurePair: Future[(StackInfo[Int], StackInfo[Int])] =
for {
beforePush <- stackActor ? Size
afterPush <- { stackActor ! Push(7); stackActor ? Peek }
} yield (beforePush, afterPush)
futurePair map { case (beforePush, afterPush) =>
assert(afterPush.top == Some(7))
assert(afterPush.size == beforePush.size + 1)
}
}
}
}
Given these behavior functions, you could invoke them directly, but AsyncFreeSpec offers a DSL for the purpose,
which looks like this:
behave like nonEmptyStackActor(almostEmptyStackActor, LastValuePushed, almostEmptyStackActorName)
Here's an example:
class StackSpec extends AsyncFreeSpec with AsyncFreeSpecStackBehaviors {
val Max = 10
val LastValuePushed = Max - 1
// Stack fixture creation methods
val emptyStackActorName = "empty stack actor"
def emptyStackActor = new StackActor[Int](Max, emptyStackActorName )
val fullStackActorName = "full stack actor"
def fullStackActor = {
val stackActor = new StackActor[Int](Max, fullStackActorName )
for (i <- 0 until Max)
stackActor ! Push(i)
stackActor
}
val almostEmptyStackActorName = "almost empty stack actor"
def almostEmptyStackActor = {
val stackActor = new StackActor[Int](Max, almostEmptyStackActorName )
stackActor ! Push(LastValuePushed)
stackActor
}
val almostFullStackActorName = "almost full stack actor"
def almostFullStackActor = {
val stackActor = new StackActor[Int](Max, almostFullStackActorName)
for (i <- 1 to LastValuePushed)
stackActor ! Push(i)
stackActor
}
"A Stack" - {
"(when empty)" - {
"should be empty" in {
val stackActor = emptyStackActor
val futureStackInfo = stackActor ? Size
futureStackInfo map { stackInfo =>
assert(stackInfo.isEmpty)
}
}
"should complain on peek" in {
recoverToSucceededIf[IllegalStateException] {
emptyStackActor ? Peek
}
}
"should complain on pop" in {
recoverToSucceededIf[IllegalStateException] {
emptyStackActor ? Pop
}
}
}
"(with one item)" - {
"should" - {
behave like nonEmptyStackActor(almostEmptyStackActor, LastValuePushed, almostEmptyStackActorName)
behave like nonFullStackActor(almostEmptyStackActor, almostEmptyStackActorName)
}
}
"(with one item less than capacity)" - {
"should" - {
behave like nonEmptyStackActor(almostFullStackActor, LastValuePushed, almostFullStackActorName)
behave like nonFullStackActor(almostFullStackActor, almostFullStackActorName)
}
}
"(full)" - {
"should be full" in {
val stackActor = fullStackActor
val futureStackInfo = stackActor ? Size
futureStackInfo map { stackInfo =>
assert(stackInfo.isFull)
}
}
"should" - {
behave like nonEmptyStackActor(fullStackActor, LastValuePushed, fullStackActorName)
}
"should complain on a push" in {
val stackActor = fullStackActor
assertThrows[IllegalStateException] {
stackActor ! Push(10)
}
}
}
}
}
If you load these classes into the Scala interpreter (with scalatest's JAR file on the class path), and execute it, you'll see:
scala> org.scalatest.run(new StackSpec)
StackSpec:
A Stack
(when empty)
- should be empty
- should complain on peek
- should complain on pop
(with one item)
should
- return non-empty StackInfo when Size is fired at non-empty stack actor: almost empty stack actor
- return before and after StackInfo that has existing size and lastItemAdded as top when Peek is fired at non-empty stack actor: almost empty stack actor
- return before and after StackInfo that has existing size - 1 and lastItemAdded as top when Pop is fired at non-empty stack actor: almost empty stack actor
- return non-full StackInfo when Size is fired at non-full stack actor: almost empty stack actor
- return before and after StackInfo that has existing size + 1 and new item as top when Push is fired at non-full stack actor: almost empty stack actor
(with one item less than capacity)
should
- return non-empty StackInfo when Size is fired at non-empty stack actor: almost full stack actor
- return before and after StackInfo that has existing size and lastItemAdded as top when Peek is fired at non-empty stack actor: almost full stack actor
- return before and after StackInfo that has existing size - 1 and lastItemAdded as top when Pop is fired at non-empty stack actor: almost full stack actor
- return non-full StackInfo when Size is fired at non-full stack actor: almost full stack actor
- return before and after StackInfo that has existing size + 1 and new item as top when Push is fired at non-full stack actor: almost full stack actor
(full)
- should be full
should
- return non-empty StackInfo when Size is fired at non-empty stack actor: full stack actor
- return before and after StackInfo that has existing size and lastItemAdded as top when Peek is fired at non-empty stack actor: full stack actor
- return before and after StackInfo that has existing size - 1 and lastItemAdded as top when Pop is fired at non-empty stack actor: full stack actor
- should complain on a push
One thing to keep in mind when using shared tests is that in ScalaTest, each test in a suite must have a unique name.
If you register the same tests repeatedly in the same suite, one problem you may encounter is an exception at runtime
complaining that multiple tests are being registered with the same test name.
Although in an AsyncFreeSpec, the - clause is a nesting construct analogous to
AsyncFunSpec's describe clause, you many sometimes need to do a bit of
extra work to ensure that the test names are unique. If a duplicate test name problem shows up in an
AsyncFreeSpec, you'll need to pass in a prefix or suffix string to add to each test name. You can call
toString on the shared fixture object, or pass this string
the same way you pass any other data needed by the shared tests.
This is the approach taken by the previous AsyncFreeSpecStackBehaviors example.
Given this AsyncFreeSpecStackBehaviors trait, calling it with the almostEmptyStackActor fixture, like this:
behave like nonEmptyStackActor(almostEmptyStackActor, LastValuePushed, almostEmptyStackActorName)
yields test names:
A Stack (when non-empty) should return non-empty StackInfo when Size is fired at non-empty stack actor: almost empty stack actorA Stack (when non-empty) should return before and after StackInfo that has existing size and lastItemAdded as top when Peek is fired at non-empty stack actor: almost empty stack actorA Stack (when non-empty) should return before and after StackInfo that has existing size - 1 and lastItemAdded as top when Pop is fired at non-empty stack actor: almost empty stack actorWhereas calling it with the almostFullStackActor fixture, like this:
behave like nonEmptyStackActor(almostFullStackActor, LastValuePushed, almostFullStackActorName)
yields different test names:
A Stack (when non-empty) should return non-empty StackInfo when Size is fired at non-empty stack actor: almost full stack actorA Stack (when non-empty) should return before and after StackInfo that has existing size and lastItemAdded as top when Peek is fired at non-empty stack actor: almost full stack actorA Stack (when non-empty) should return before and after StackInfo that has existing size - 1 and lastItemAdded as top when Pop is fired at non-empty stack actor: almost full stack actor
Implementation trait for class AsyncFreeSpec, which
facilitates a “behavior-driven” style of development (BDD),
in which tests are nested inside text clauses denoted with the dash
operator (-).
Implementation trait for class AsyncFreeSpec, which
facilitates a “behavior-driven” style of development (BDD),
in which tests are nested inside text clauses denoted with the dash
operator (-).
AsyncFreeSpec is a class, not a trait,
to minimize compile time given there is a slight compiler overhead to
mixing in traits compared to extending classes. If you need to mix the
behavior of AsyncFreeSpec into some other class, you can use this
trait instead, because class AsyncFreeSpec does nothing more than
extend this trait and add a nice toString implementation.
See the documentation of the class for a detailed
overview of AsyncFreeSpec.
A sister class to org.scalatest.freespec.AnyFreeSpec that can pass a fixture object into its tests.
A sister class to org.scalatest.freespec.AnyFreeSpec that can pass a fixture object into its tests.
Recommended Usage:
Use class FixtureAnyFreeSpec in situations for which AnyFreeSpec
would be a good choice, when all or most tests need the same fixture objects
that must be cleaned up afterwards. Note: FixtureAnyFreeSpec is intended for use in special situations, with class AnyFreeSpec used for general needs. For
more insight into where FixtureAnyFreeSpec fits in the big picture, see the withFixture(OneArgTest) subsection of the Shared fixtures section in the documentation for class AnyFreeSpec.
|
Class FixtureAnyFreeSpec behaves similarly to class org.scalatest.freespec.AnyFreeSpec, except that tests may have a
fixture parameter. The type of the
fixture parameter is defined by the abstract FixtureParam type, which is a member of this class.
This class also has an abstract withFixture method. This withFixture method
takes a OneArgTest, which is a nested trait defined as a member of this class.
OneArgTest has an apply method that takes a FixtureParam.
This apply method is responsible for running a test.
This class's runTest method delegates the actual running of each test to withFixture(OneArgTest), passing
in the test code to run via the OneArgTest argument. The withFixture(OneArgTest) method (abstract in this class) is responsible
for creating the fixture argument and passing it to the test function.
Subclasses of this class must, therefore, do three things differently from a plain old org.scalatest.freespec.AnyFreeSpec:
FixtureParamwithFixture(OneArgTest) methodIf the fixture you want to pass into your tests consists of multiple objects, you will need to combine them into one object to use this class. One good approach to passing multiple fixture objects is to encapsulate them in a case class. Here's an example:
case class FixtureParam(file: File, writer: FileWriter)
To enable the stacking of traits that define withFixture(NoArgTest), it is a good idea to let
withFixture(NoArgTest) invoke the test function instead of invoking the test
function directly. To do so, you'll need to convert the OneArgTest to a NoArgTest. You can do that by passing
the fixture object to the toNoArgTest method of OneArgTest. In other words, instead of
writing “test(theFixture)”, you'd delegate responsibility for
invoking the test function to the withFixture(NoArgTest) method of the same instance by writing:
withFixture(test.toNoArgTest(theFixture))
Here's a complete example:
package org.scalatest.examples.freespec.oneargtest
import org.scalatest.freespec
import java.io._
class ExampleSpec extends freespec.FixtureAnyFreeSpec {
case class FixtureParam(file: File, writer: FileWriter)
def withFixture(test: OneArgTest) = {
// create the fixture
val file = File.createTempFile("hello", "world")
val writer = new FileWriter(file)
val theFixture = FixtureParam(file, writer)
try {
writer.write("ScalaTest is ") // set up the fixture
withFixture(test.toNoArgTest(theFixture)) // "loan" the fixture to the test
}
finally writer.close() // clean up the fixture
}
"Testing" - {
"should be easy" in { f =>
f.writer.write("easy!")
f.writer.flush()
assert(f.file.length === 18)
}
"should be fun" in { f =>
f.writer.write("fun!")
f.writer.flush()
assert(f.file.length === 17)
}
}
}
If a test fails, the OneArgTest function will result in a Failed wrapping the exception describing the failure.
To ensure clean up happens even if a test fails, you should invoke the test function from inside a try block and do the cleanup in a
finally clause, as shown in the previous example.
If multiple test classes need the same fixture, you can define the FixtureParam and withFixture(OneArgTest) implementations
in a trait, then mix that trait into the test classes that need it. For example, if your application requires a database and your integration tests
use that database, you will likely have many test classes that need a database fixture. You can create a "database fixture" trait that creates a
database with a unique name, passes the connector into the test, then removes the database once the test completes. This is shown in the following example:
package org.scalatest.examples.fixture.freespec.sharing
import java.util.concurrent.ConcurrentHashMap
import org.scalatest.fixture
import DbServer._
import java.util.UUID.randomUUID
object DbServer { // Simulating a database server
type Db = StringBuffer
private val databases = new ConcurrentHashMap[String, Db]
def createDb(name: String): Db = {
val db = new StringBuffer
databases.put(name, db)
db
}
def removeDb(name: String) {
databases.remove(name)
}
}
trait DbFixture { this: fixture.Suite =>
type FixtureParam = Db
// Allow clients to populate the database after
// it is created
def populateDb(db: Db) {}
def withFixture(test: OneArgTest) = {
val dbName = randomUUID.toString
val db = createDb(dbName) // create the fixture
try {
populateDb(db) // setup the fixture
withFixture(test.toNoArgTest(db)) // "loan" the fixture to the test
}
finally removeDb(dbName) // clean up the fixture
}
}
class ExampleSpec extends FixtureAnyFreeSpec with DbFixture {
override def populateDb(db: Db) { // setup the fixture
db.append("ScalaTest is ")
}
"Testing" - {
"should be easy" in { db =>
db.append("easy!")
assert(db.toString === "ScalaTest is easy!")
}
"should be fun" in { db =>
db.append("fun!")
assert(db.toString === "ScalaTest is fun!")
}
}
// This test doesn't need a Db
"Test code" - {
"should be clear" in { () =>
val buf = new StringBuffer
buf.append("ScalaTest code is ")
buf.append("clear!")
assert(buf.toString === "ScalaTest code is clear!")
}
}
}
Often when you create fixtures in a trait like DbFixture, you'll still need to enable individual test classes
to "setup" a newly created fixture before it gets passed into the tests. A good way to accomplish this is to pass the newly
created fixture into a setup method, like populateDb in the previous example, before passing it to the test
function. Classes that need to perform such setup can override the method, as does ExampleSpec.
If a test doesn't need the fixture, you can indicate that by providing a no-arg instead of a one-arg function, as is done in the
third test in the previous example, “Test code should be clear”. In other words, instead of starting your function literal
with something like “db =>”, you'd start it with “() =>”. For such tests, runTest
will not invoke withFixture(OneArgTest). It will instead directly invoke withFixture(NoArgTest).
Both examples shown above demonstrate the technique of giving each test its own "fixture sandbox" to play in. When your fixtures
involve external side-effects, like creating files or databases, it is a good idea to give each file or database a unique name as is
done in these examples. This keeps tests completely isolated, allowing you to run them in parallel if desired. You could mix
ParallelTestExecution into either of these ExampleSpec classes, and the tests would run in parallel just fine.
Implementation trait for class FixtureAnyFreeSpec, which is
a sister class to org.scalatest.freespec.AnyFreeSpec that can pass a
fixture object into its tests.
Implementation trait for class FixtureAnyFreeSpec, which is
a sister class to org.scalatest.freespec.AnyFreeSpec that can pass a
fixture object into its tests.
FixtureAnyFreeSpec is a class,
not a trait, to minimize compile time given there is a slight compiler
overhead to mixing in traits compared to extending classes. If you need
to mix the behavior of FixtureAnyFreeSpec into some other
class, you can use this trait instead, because class
FixtureAnyFreeSpec does nothing more than extend this trait and add a nice toString implementation.
See the documentation of the class for a detailed
overview of FixtureAnyFreeSpec.
A sister class to org.scalatest.freespec.AsyncFreeSpec that can pass a fixture object into its tests.
A sister class to org.scalatest.freespec.AsyncFreeSpec that can pass a fixture object into its tests.
Recommended Usage:
Use class FixtureAsyncFunSpec in situations for which AsyncFreeSpec
would be a good choice, when all or most tests need the same fixture objects
that must be cleaned up afterwards. Note: FixtureAsyncFreeSpec is intended for use in special situations, with class AsyncFreeSpec used for general needs. For
more insight into where FixtureAsyncFreeSpec fits in the big picture, see the withFixture(OneArgAsyncTest) subsection of the Shared fixtures section in the documentation for class AsyncFunSpec.
|
Class FixtureAsyncFreeSpec behaves similarly to class org.scalatest.freespec.AsyncFreeSpec, except that tests may have a
fixture parameter. The type of the
fixture parameter is defined by the abstract FixtureParam type, which is a member of this class.
This class also contains an abstract withFixture method. This withFixture method
takes a OneArgAsyncTest, which is a nested trait defined as a member of this class.
OneArgAsyncTest has an apply method that takes a FixtureParam.
This apply method is responsible for running a test.
This class's runTest method delegates the actual running of each test to withFixture(OneArgAsyncTest), passing
in the test code to run via the OneArgAsyncTest argument. The withFixture(OneArgAsyncTest) method (abstract in this class) is responsible
for creating the fixture argument and passing it to the test function.
Subclasses of this class must, therefore, do three things differently from a plain old org.scalatest.freespec.AsyncFunSpec:
FixtureParamwithFixture(OneArgAsyncTest) methodIf the fixture you want to pass into your tests consists of multiple objects, you will need to combine them into one object to use this class. One good approach to passing multiple fixture objects is to encapsulate them in a case class. Here's an example:
case class FixtureParam(file: File, writer: FileWriter)
To enable the stacking of traits that define withFixture(NoArgAsyncTest), it is a good idea to let
withFixture(NoArgAsyncTest) invoke the test function instead of invoking the test
function directly. To do so, you'll need to convert the OneArgAsyncTest to a NoArgAsyncTest. You can do that by passing
the fixture object to the toNoArgAsyncTest method of OneArgAsyncTest. In other words, instead of
writing “test(theFixture)”, you'd delegate responsibility for
invoking the test function to the withFixture(NoArgAsyncTest) method of the same instance by writing:
withFixture(test.toNoArgAsyncTest(theFixture))
Here's a complete example:
package org.scalatest.examples.asyncfreespec.oneargasynctest
import org.scalatest._
import scala.concurrent.Future
import scala.concurrent.ExecutionContext
// Defining actor messages
sealed abstract class StringOp
case object Clear extends StringOp
case class Append(value: String) extends StringOp
case object GetValue
class StringActor { // Simulating an actor
private final val sb = new StringBuilder
def !(op: StringOp): Unit =
synchronized {
op match {
case Append(value) => sb.append(value)
case Clear => sb.clear()
}
}
def ?(get: GetValue.type)(implicit c: ExecutionContext): Future[String] =
Future {
synchronized { sb.toString }
}
}
class ExampleSpec extends freespec.FixtureAsyncFreeSpec {
type FixtureParam = StringActor
def withFixture(test: OneArgAsyncTest): FutureOutcome = {
val actor = new StringActor
complete {
actor ! Append("ScalaTest is ") // set up the fixture
withFixture(test.toNoArgAsyncTest(actor))
} lastly {
actor ! Clear // ensure the fixture will be cleaned up
}
}
"Testing" - {
"should be easy" in { actor =>
actor ! Append("easy!")
val futureString = actor ? GetValue
futureString map { s =>
assert(s == "ScalaTest is easy!")
}
}
"should be fun" in { actor =>
actor ! Append("fun!")
val futureString = actor ? GetValue
futureString map { s =>
assert(s == "ScalaTest is fun!")
}
}
}
}
If a test fails, the future returned by the OneArgAsyncTest function will result in
an org.scalatest.Failed wrapping the exception describing
the failure. To ensure clean up happens even if a test fails, you should invoke the test function and do the cleanup using
complete-lastly, as shown in the previous example. The complete-lastly syntax, defined in CompleteLastly, which is extended by AsyncTestSuite, ensures
the second, cleanup block of code is executed, whether the the first block throws an exception or returns a future. If it returns a
future, the cleanup will be executed when the future completes.
If multiple test classes need the same fixture, you can define the FixtureParam and withFixture(OneArgAsyncTest)
implementations in a trait, then mix that trait into the test classes that need it. For example, if your application requires a database and your
integration tests use that database, you will likely have many test classes that need a database fixture. You can create a "database fixture" trait
that creates a database with a unique name, passes the connector into the test, then removes the database once the test completes. This is shown in
the following example:
package org.scalatest.examples.fixture.asyncfreespec.sharing
import java.util.concurrent.ConcurrentHashMap
import org.scalatest._
import DbServer._
import java.util.UUID.randomUUID
import scala.concurrent.Future
object DbServer { // Simulating a database server
type Db = StringBuffer
private val databases = new ConcurrentHashMap[String, Db]
def createDb(name: String): Db = {
val db = new StringBuffer
databases.put(name, db)
db
}
def removeDb(name: String) {
databases.remove(name)
}
}
trait DbFixture { this: fixture.AsyncTestSuite =>
type FixtureParam = Db
// Allow clients to populate the database after
// it is created
def populateDb(db: Db) {}
def withFixture(test: OneArgAsyncTest): FutureOutcome = {
val dbName = randomUUID.toString
val db = createDb(dbName) // create the fixture
complete {
populateDb(db) // setup the fixture
withFixture(test.toNoArgAsyncTest(db)) // "loan" the fixture to the test
} lastly {
removeDb(dbName) // ensure the fixture will be cleaned up
}
}
}
class ExampleSpec extends freespec.FixtureAsyncFreeSpec with DbFixture {
override def populateDb(db: Db) { // setup the fixture
db.append("ScalaTest is ")
}
"Testing" - {
"should be easy" in { db =>
Future {
db.append("easy!")
assert(db.toString === "ScalaTest is easy!")
}
}
"should be fun" in { db =>
Future {
db.append("fun!")
assert(db.toString === "ScalaTest is fun!")
}
}
// This test doesn't need a Db
"code should be clear" in { () =>
Future {
val buf = new StringBuffer
buf.append("ScalaTest code is ")
buf.append("clear!")
assert(buf.toString === "ScalaTest code is clear!")
}
}
}
}
Often when you create fixtures in a trait like DbFixture, you'll still need to enable individual test classes
to "setup" a newly created fixture before it gets passed into the tests. A good way to accomplish this is to pass the newly
created fixture into a setup method, like populateDb in the previous example, before passing it to the test
function. Classes that need to perform such setup can override the method, as does ExampleSuite.
If a test doesn't need the fixture, you can indicate that by providing a no-arg instead of a one-arg function, as is done in the
third test in the previous example, “test code should be clear”. In other words, instead of starting your function literal
with something like “db =>”, you'd start it with “() =>”. For such tests, runTest
will not invoke withFixture(OneArgAsyncTest). It will instead directly invoke withFixture(NoArgAsyncTest).
Both examples shown above demonstrate the technique of giving each test its own "fixture sandbox" to play in. When your fixtures
involve external side-effects, like creating files or databases, it is a good idea to give each file or database a unique name as is
done in these examples. This keeps tests completely isolated, allowing you to run them in parallel if desired. You could mix
ParallelTestExecution into either of these ExampleSuite classes, and the tests would run in parallel just fine.
Implementation trait for class FixtureAsyncFreeSpec, which is
a sister class to org.scalatest.freespec.AsyncFreeSpec that can pass a
fixture object into its tests.
Implementation trait for class FixtureAsyncFreeSpec, which is
a sister class to org.scalatest.freespec.AsyncFreeSpec that can pass a
fixture object into its tests.
FixtureAsyncFreeSpec is a class,
not a trait, to minimize compile time given there is a slight compiler
overhead to mixing in traits compared to extending classes. If you need
to mix the behavior of FixtureAsyncFreeSpec into some other
class, you can use this trait instead, because class
FixtureAsyncFreeSpec does nothing more than extend this trait and add a nice toString implementation.
See the documentation of the class for a detailed
overview of FixtureAsyncFreeSpec.
Facilitates a “behavior-driven” style of development (BDD), in which tests are nested inside text clauses denoted with the dash operator (
-).AnyFreeSpecis so named because unlike classes such asAnyWordSpec,AnyFlatSpec, andAnyFunSpec, it is enforces no structure on the text. You are free to compose text however you like. (AAnyFreeSpecis like free-verse poetry as opposed to a sonnet or haiku, which defines a structure for the text of the poem.)AnyFreeSpecis a good choice for teams experienced with BDD and able to agree on how to structure the specification text.Here's an example
AnyFreeSpec:package org.scalatest.examples.freespec import org.scalatest.freespec.AnyFreeSpec class SetSpec extends AnyFreeSpec { "A Set" - { "when empty" - { "should have size 0" in { assert(Set.empty.size === 0) } "should produce NoSuchElementException when head is invoked" in { assertThrows[NoSuchElementException] { Set.empty.head } } } } }In a
AnyFreeSpecyou write a test with a string followed byinand the body of the test in curly braces, like this:"should have size 0" in { // ... }You can nest a test inside any number of description clauses, which you write with a string followed by a dash character and a block, like this:
"A Set" - { // ... }You can nest description clauses as deeply as you want. Because the description clause is denoted with an operator, not a word like
should, you are free to structure the text however you wish. Here's an example:import org.scalatest.freespec.AnyFreeSpec class StackSpec extends AnyFreeSpec { "A Stack" - { "whenever it is empty" - { "certainly ought to" - { "be empty" in { // ... } "complain on peek" in { // ... } "complain on pop" in { // ... } } } "but when full, by contrast, must" - { "be full" in { // ... } "complain on push" in { // ... } } } }Running the above
StackSpecin the interpreter would yield:scala> org.scalatest.run(new StackSpec) StackSpec: A Stack whenever it is empty certainly ought to - be empty - complain on peek - complain on pop but when full, by contrast, must - be full - complain on pushA
AnyFreeSpeccan also be used to write a specification-style test in languages other than English. For example:import org.scalatest.freespec.AnyFreeSpec class ComputerRoomRulesSpec extends AnyFreeSpec { "Achtung!" - { "Alle touristen und non-technischen lookenpeepers!" - { "Das machine is nicht fuer fingerpoken und mittengrabben." in { // ... } "Is easy" - { "schnappen der springenwerk" in { // ... } "blowenfusen" in { // ... } "und poppencorken mit spitzen sparken." in { // ... } } "Das machine is diggen by experten only." in { // ... } "Is nicht fuer gerwerken by das dummkopfen." in { // ... } "Das rubbernecken sightseeren keepen das cottenpicken hands in das pockets." in { // ... } "Relaxen und watchen das blinkenlights." in { // ... } } } }Running the above
ComputerRoomRulesSpecin the interpreter would yield:scala> org.scalatest.run(new ComputerRoomRulesSpec) ComputerRoomRulesSpec: Achtung! Alle touristen und non-technischen lookenpeepers! - Das machine is nicht fuer fingerpoken und mittengrabben. Is easy - schnappen der springenwerk - blowenfusen - und poppencorken mit spitzen sparken. - Das machine is diggen by experten only. - Is nicht fuer gerwerken by das dummkopfen. - Das rubbernecken sightseeren keepen das cottenpicken hands in das pockets. - Relaxen und watchen das blinkenlights.A
AnyFreeSpec's lifecycle has two phases: the registration phase and the ready phase. It starts in registration phase and enters ready phase the first timerunis called on it. It then remains in ready phase for the remainder of its lifetime.Tests can only be registered while the
AnyFreeSpecis in its registration phase. Any attempt to register a test after theAnyFreeSpechas entered its ready phase, i.e., afterrunhas been invoked on theAnyFreeSpec, will be met with a thrownTestRegistrationClosedException. The recommended style of usingAnyFreeSpecis to register tests during object construction as is done in all the examples shown here. If you keep to the recommended style, you should never see aTestRegistrationClosedException.Ignored tests
To support the common use case of temporarily disabling a test, with the good intention of resurrecting the test at a later time,
AnyFreeSpecadds a methodignoreto strings that can be used instead ofinto register a test. For example, to temporarily disable the test with the name"A Stack should pop values in last-in-first-out order", just change “in” into “ignore,” like this:package org.scalatest.examples.freespec.ignore import org.scalatest.freespec.AnyFreeSpec class SetSpec extends AnyFreeSpec { "A Set" - { "when empty" - { "should have size 0" ignore { assert(Set.empty.size === 0) } "should produce NoSuchElementException when head is invoked" in { assertThrows[NoSuchElementException] { Set.empty.head } } } } }If you run this version of
SetSpecwith:It will run only the second test and report that the first test was ignored:
If you wish to temporarily ignore an entire suite of tests, you can (on the JVM, not Scala.js) annotate the test class with
@Ignore, like this:package org.scalatest.examples.freespec.ignoreall import org.scalatest.freespec.AnyFreeSpec import org.scalatest.Ignore @Ignore class SetSpec extends AnyFreeSpec { "A Set" - { "when empty" - { "should have size 0" in { assert(Set.empty.size === 0) } "should produce NoSuchElementException when head is invoked" in { assertThrows[NoSuchElementException] { Set.empty.head } } } } }When you mark a test class with a tag annotation, ScalaTest will mark each test defined in that class with that tag. Thus, marking the
SetSpecin the above example with the@Ignoretag annotation means that both tests in the class will be ignored. If you run the aboveSetSpecin the Scala interpreter, you'll see:Note that marking a test class as ignored won't prevent it from being discovered by ScalaTest. Ignored classes will be discovered and run, and all their tests will be reported as ignored. This is intended to keep the ignored class visible, to encourage the developers to eventually fix and “un-ignore” it. If you want to prevent a class from being discovered at all (on the JVM, not Scala.js), use the
DoNotDiscoverannotation instead.Informers
One of the parameters to
AnyFreeSpec'srunmethod is aReporter, which will collect and report information about the running suite of tests. Information about suites and tests that were run, whether tests succeeded or failed, and tests that were ignored will be passed to theReporteras the suite runs. Most often the reporting done by default byAnyFreeSpec's methods will be sufficient, but occasionally you may wish to provide custom information to theReporterfrom a test. For this purpose, anInformerthat will forward information to the currentReporteris provided via theinfoparameterless method. You can pass the extra information to theInformervia itsapplymethod. TheInformerwill then pass the information to theReportervia anInfoProvidedevent.One use case for the
Informeris to pass more information about a specification to the reporter. For example, theGivenWhenThentrait provides methods that use the implicitinfoprovided byAnyFreeSpecto pass such information to the reporter. Here's an example:package org.scalatest.examples.freespec.info import collection.mutable import org.scalatest._ class SetSpec extends freespec.AnyFreeSpec with GivenWhenThen { "A mutable Set" - { "should allow an element to be added" in { Given("an empty mutable Set") val set = mutable.Set.empty[String] When("an element is added") set += "clarity" Then("the Set should have size 1") assert(set.size === 1) And("the Set should contain the added element") assert(set.contains("clarity")) info("That's all folks!") } } }If you run this
AnyFreeSpecfrom the interpreter, you will see the following output:scala> org.scalatest.run(new SetSpec) A mutable Set - should allow an element to be added + Given an empty mutable Set + When an element is added + Then the Set should have size 1 + And the Set should contain the added element + That's all folks!Documenters
AnyFreeSpecalso provides amarkupmethod that returns aDocumenter, which allows you to send to theReportertext formatted in Markdown syntax. You can pass the extra information to theDocumentervia itsapplymethod. TheDocumenterwill then pass the information to theReportervia anMarkupProvidedevent.Here's an example
AnyFreeSpecthat usesmarkup:package org.scalatest.examples.freespec.markup import collection.mutable import org.scalatest._ class SetSpec extends freespec.AnyFreeSpec with GivenWhenThen { markup { """ Mutable Set ----------- A set is a collection that contains no duplicate elements. To implement a concrete mutable set, you need to provide implementations of the following methods: def contains(elem: A): Boolean def iterator: Iterator[A] def += (elem: A): this.type def -= (elem: A): this.type If you wish that methods like `take`, `drop`, `filter` return the same kind of set, you should also override: def empty: This It is also good idea to override methods `foreach` and `size` for efficiency. """ } "A mutable Set" - { "should allow an element to be added" in { Given("an empty mutable Set") val set = mutable.Set.empty[String] When("an element is added") set += "clarity" Then("the Set should have size 1") assert(set.size === 1) And("the Set should contain the added element") assert(set.contains("clarity")) markup("This test finished with a **bold** statement!") } } }Although all of ScalaTest's built-in reporters will display the markup text in some form, the HTML reporter will format the markup information into HTML. Thus, the main purpose of
markupis to add nicely formatted text to HTML reports. Here's what the aboveSetSpecwould look like in the HTML reporter:Notifiers and alerters
ScalaTest records text passed to
infoandmarkupduring tests, and sends the recorded text in therecordedEventsfield of test completion events likeTestSucceededandTestFailed. This allows string reporters (like the standard out reporter) to showinfoandmarkuptext after the test name in a color determined by the outcome of the test. For example, if the test fails, string reporters will show theinfoandmarkuptext in red. If a test succeeds, string reporters will show theinfoandmarkuptext in green. While this approach helps the readability of reports, it means that you can't useinfoto get status updates from long running tests.To get immediate (i.e., non-recorded) notifications from tests, you can use
note(aNotifier) andalert(anAlerter). Here's an example showing the differences:package org.scalatest.examples.freespec.note import collection.mutable import org.scalatest._ class SetSpec extends freespec.AnyFreeSpec { "A mutable Set" - { "should allow an element to be added" in { info("info is recorded") markup("markup is *also* recorded") note("notes are sent immediately") alert("alerts are also sent immediately") val set = mutable.Set.empty[String] set += "clarity" assert(set.size === 1) assert(set.contains("clarity")) } } }Another example is slowpoke notifications. If you find a test is taking a long time to complete, but you're not sure which test, you can enable slowpoke notifications. ScalaTest will use an
Alerterto fire an event whenever a test has been running longer than a specified amount of time.In summary, use
infoandmarkupfor text that should form part of the specification output. Usenoteandalertto send status notifications. (Because the HTML reporter is intended to produce a readable, printable specification,infoandmarkuptext will appear in the HTML report, butnoteandalerttext will not.)Pending tests
A pending test is one that has been given a name but is not yet implemented. The purpose of pending tests is to facilitate a style of testing in which documentation of behavior is sketched out before tests are written to verify that behavior (and often, before the behavior of the system being tested is itself implemented). Such sketches form a kind of specification of what tests and functionality to implement later.
To support this style of testing, a test can be given a name that specifies one bit of behavior required by the system being tested. The test can also include some code that sends more information about the behavior to the reporter when the tests run. At the end of the test, it can call method
pending, which will cause it to complete abruptly withTestPendingException.Because tests in ScalaTest can be designated as pending with
TestPendingException, both the test name and any information sent to the reporter when running the test can appear in the report of a test run. (In other words, the code of a pending test is executed just like any other test.) However, because the test completes abruptly withTestPendingException, the test will be reported as pending, to indicate the actual test, and possibly the functionality it is intended to test, has not yet been implemented. You can mark tests as pending in aAnyFreeSpeclike this:package org.scalatest.examples.freespec.pending import org.scalatest._ class SetSpec extends freespec.AnyFreeSpec { "A Set" - { "when empty" - { "should have size 0" in (pending) "should produce NoSuchElementException when head is invoked" in { assertThrows[NoSuchElementException] { Set.empty.head } } } } }If you run this version of
SetSpecwith:It will run both tests but report that
should have size 0is pending. You'll see:One difference between an ignored test and a pending one is that an ignored test is intended to be used during a significant refactorings of the code under test, when tests break and you don't want to spend the time to fix all of them immediately. You can mark some of those broken tests as ignored temporarily, so that you can focus the red bar on just failing tests you actually want to fix immediately. Later you can go back and fix the ignored tests. In other words, by ignoring some failing tests temporarily, you can more easily notice failed tests that you actually want to fix. By contrast, a pending test is intended to be used before a test and/or the code under test is written. Pending indicates you've decided to write a test for a bit of behavior, but either you haven't written the test yet, or have only written part of it, or perhaps you've written the test but don't want to implement the behavior it tests until after you've implemented a different bit of behavior you realized you need first. Thus ignored tests are designed to facilitate refactoring of existing code whereas pending tests are designed to facilitate the creation of new code.
One other difference between ignored and pending tests is that ignored tests are implemented as a test tag that is excluded by default. Thus an ignored test is never executed. By contrast, a pending test is implemented as a test that throws
TestPendingException(which is what calling thependingmethod does). Thus the body of pending tests are executed up until they throwTestPendingException. The reason for this difference is that it enables your unfinished test to sendInfoProvidedmessages to the reporter before it completes abruptly withTestPendingException, as shown in the previous example onInformers that used theGivenWhenThentrait. For example, the following snippet in aAnyFreeSpec:"The Scala language" - { "should add correctly" in { Given("two integers") When("they are added") Then("the result is the sum of the two numbers") pending } // ...Would yield the following output when run in the interpreter:
Tagging tests
A
AnyFreeSpec's tests may be classified into groups by tagging them with string names. As with any suite, when executing aAnyFreeSpec, groups of tests can optionally be included and/or excluded. To tag aAnyFreeSpec's tests, you pass objects that extend classorg.scalatest.Tagto methods that register tests. ClassTagtakes one parameter, a string name. If you have created tag annotation interfaces as described in theTagdocumentation, then you will probably want to use tag names on your test functions that match. To do so, simply pass the fully qualified names of the tag interfaces to theTagconstructor. For example, if you've defined a tag annotation interface with fully qualified name,com.mycompany.tags.DbTest, then you could create a matching tag forAnyFreeSpecs like this:import org.scalatest.Tag object DbTest extends Tag("com.mycompany.tags.DbTest")Given these definitions, you could tag
AnyFreeSpectests like this:package org.scalatest.examples.freespec.tagging import org.scalatest.Tag object DbTest extends Tag("com.mycompany.tags.DbTest") import org.scalatest.freespec.AnyFreeSpec import org.scalatest.tagobjects.Slow class SetSpec extends AnyFreeSpec { "A Set" - { "when empty" - { "should have size 0" taggedAs(Slow) in { assert(Set.empty.size === 0) } "should produce NoSuchElementException when head is invoked" taggedAs(Slow, DbTest) in { assertThrows[NoSuchElementException] { Set.empty.head } } } } }This code marks both tests with the
org.scalatest.tags.Slowtag, and the second test with thecom.mycompany.tags.DbTesttag.The
runmethod takes aFilter, whose constructor takes an optionalSet[String]calledtagsToIncludeand aSet[String]calledtagsToExclude. IftagsToIncludeisNone, all tests will be run except those those belonging to tags listed in thetagsToExcludeSet. IftagsToIncludeis defined, only tests belonging to tags mentioned in thetagsToIncludeset, and not mentioned intagsToExclude, will be run.It is recommended, though not required, that you create a corresponding tag annotation when you create a
Tagobject. A tag annotation (on the JVM, not Scala.js) allows you to tag all the tests of aAnyFreeSpecin one stroke by annotating the class. For more information and examples, see the documentation for classTag. On Scala.js, to tag all tests of a suite, you'll need to tag each test individually at the test site.Shared fixtures
A test fixture is composed of the objects and other artifacts (files, sockets, database connections, etc.) tests use to do their work. When multiple tests need to work with the same fixtures, it is important to try and avoid duplicating the fixture code across those tests. The more code duplication you have in your tests, the greater drag the tests will have on refactoring the actual production code.
ScalaTest recommends three techniques to eliminate such code duplication:
withFixtureEach technique is geared towards helping you reduce code duplication without introducing instance
vars, shared mutable objects, or other dependencies between tests. Eliminating shared mutable state across tests will make your test code easier to reason about and more amenable for parallel test execution.The following sections describe these techniques, including explaining the recommended usage for each. But first, here's a table summarizing the options:
withFixturewhen most or all tests need the same fixture.withFixture(NoArgTest)withFixture(OneArgTest)instead)withFixture(OneArgTest)BeforeAndAfterBeforeAndAfterEachCalling get-fixture methods
If you need to create the same mutable fixture objects in multiple tests, and don't need to clean them up after using them, the simplest approach is to write one or more get-fixture methods. A get-fixture method returns a new instance of a needed fixture object (or an holder object containing multiple fixture objects) each time it is called. You can call a get-fixture method at the beginning of each test that needs the fixture, storing the returned object or objects in local variables. Here's an example:
package org.scalatest.examples.freespec.getfixture import org.scalatest.freespec.AnyFreeSpec import collection.mutable.ListBuffer class ExampleSpec extends AnyFreeSpec { class Fixture { val builder = new StringBuilder("ScalaTest is ") val buffer = new ListBuffer[String] } def fixture = new Fixture "Testing" - { "should be easy" in { val f = fixture f.builder.append("easy!") assert(f.builder.toString === "ScalaTest is easy!") assert(f.buffer.isEmpty) f.buffer += "sweet" } "should be fun" in { val f = fixture f.builder.append("fun!") assert(f.builder.toString === "ScalaTest is fun!") assert(f.buffer.isEmpty) } } }The “
f.” in front of each use of a fixture object provides a visual indication of which objects are part of the fixture, but if you prefer, you can import the the members with “import f._” and use the names directly.If you need to configure fixture objects differently in different tests, you can pass configuration into the get-fixture method. For example, if you could pass in an initial value for a mutable fixture object as a parameter to the get-fixture method.
Instantiating fixture-context objects
An alternate technique that is especially useful when different tests need different combinations of fixture objects is to define the fixture objects as instance variables of fixture-context objects whose instantiation forms the body of tests. Like get-fixture methods, fixture-context objects are only appropriate if you don't need to clean up the fixtures after using them.
To use this technique, you define instance variables intialized with fixture objects in traits and/or classes, then in each test instantiate an object that contains just the fixture objects needed by the test. Traits allow you to mix together just the fixture objects needed by each test, whereas classes allow you to pass data in via a constructor to configure the fixture objects. Here's an example in which fixture objects are partitioned into two traits and each test just mixes together the traits it needs:
package org.scalatest.examples.freespec.fixturecontext import collection.mutable.ListBuffer import org.scalatest.freespec.AnyFreeSpec class ExampleSpec extends AnyFreeSpec { trait Builder { val builder = new StringBuilder("ScalaTest is ") } trait Buffer { val buffer = ListBuffer("ScalaTest", "is") } "Testing" - { // This test needs the StringBuilder fixture "should be productive" in new Builder { builder.append("productive!") assert(builder.toString === "ScalaTest is productive!") } } "Test code" - { // This test needs the ListBuffer[String] fixture "should be readable" in new Buffer { buffer += ("readable!") assert(buffer === List("ScalaTest", "is", "readable!")) } // This test needs both the StringBuilder and ListBuffer "should be clear and concise" in new Builder with Buffer { builder.append("clear!") buffer += ("concise!") assert(builder.toString === "ScalaTest is clear!") assert(buffer === List("ScalaTest", "is", "concise!")) } } }Overriding
withFixture(NoArgTest)Although the get-fixture method and fixture-context object approaches take care of setting up a fixture at the beginning of each test, they don't address the problem of cleaning up a fixture at the end of the test. If you just need to perform a side-effect at the beginning or end of a test, and don't need to actually pass any fixture objects into the test, you can override
withFixture(NoArgTest), one of ScalaTest's lifecycle methods defined in traitSuite.Trait
Suite's implementation ofrunTestpasses a no-arg test function towithFixture(NoArgTest). It iswithFixture's responsibility to invoke that test function.Suite's implementation ofwithFixturesimply invokes the function, like this:// Default implementation in trait Suite protected def withFixture(test: NoArgTest) = { test() }You can, therefore, override
withFixtureto perform setup before and/or cleanup after invoking the test function. If you have cleanup to perform, you should invoke the test function inside atryblock and perform the cleanup in afinallyclause, in case an exception propagates back throughwithFixture. (If a test fails because of an exception, the test function invoked by withFixture will result in aFailedwrapping the exception. Nevertheless, best practice is to perform cleanup in a finally clause just in case an exception occurs.)The
withFixturemethod is designed to be stacked, and to enable this, you should always call thesuperimplementation ofwithFixture, and let it invoke the test function rather than invoking the test function directly. In other words, instead of writing “test()”, you should write “super.withFixture(test)”, like this:// Your implementation override def withFixture(test: NoArgTest) = { // Perform setup try super.withFixture(test) // Invoke the test function finally { // Perform cleanup } }Here's an example in which
withFixture(NoArgTest)is used to take a snapshot of the working directory if a test fails, and send that information to the reporter:package org.scalatest.examples.freespec.noargtest import java.io.File import org.scalatest._ class ExampleSpec extends freespec.AnyFreeSpec { override def withFixture(test: NoArgTest) = { super.withFixture(test) match { case failed: Failed => val currDir = new File(".") val fileNames = currDir.list() info("Dir snapshot: " + fileNames.mkString(", ")) failed case other => other } } "This test" - { "should succeed" in { assert(1 + 1 === 2) } "should fail" in { assert(1 + 1 === 3) } } }Running this version of
ExampleSuitein the interpreter in a directory with two files,hello.txtandworld.txtwould give the following output:Note that the
NoArgTestpassed towithFixture, in addition to anapplymethod that executes the test, also includes the test name and the config map passed torunTest. Thus you can also use the test name and configuration objects in yourwithFixtureimplementation.Calling loan-fixture methods
If you need to both pass a fixture object into a test and perform cleanup at the end of the test, you'll need to use the loan pattern. If different tests need different fixtures that require cleanup, you can implement the loan pattern directly by writing loan-fixture methods. A loan-fixture method takes a function whose body forms part or all of a test's code. It creates a fixture, passes it to the test code by invoking the function, then cleans up the fixture after the function returns.
The following example shows three tests that use two fixtures, a database and a file. Both require cleanup after, so each is provided via a loan-fixture method. (In this example, the database is simulated with a
StringBuffer.)package org.scalatest.examples.freespec.loanfixture import java.util.concurrent.ConcurrentHashMap object DbServer { // Simulating a database server type Db = StringBuffer private val databases = new ConcurrentHashMap[String, Db] def createDb(name: String): Db = { val db = new StringBuffer databases.put(name, db) db } def removeDb(name: String) { databases.remove(name) } } import org.scalatest.freespec.AnyFreeSpec import DbServer._ import java.util.UUID.randomUUID import java.io._ class ExampleSpec extends AnyFreeSpec { def withDatabase(testCode: Db => Any) { val dbName = randomUUID.toString val db = createDb(dbName) // create the fixture try { db.append("ScalaTest is ") // perform setup testCode(db) // "loan" the fixture to the test } finally removeDb(dbName) // clean up the fixture } def withFile(testCode: (File, FileWriter) => Any) { val file = File.createTempFile("hello", "world") // create the fixture val writer = new FileWriter(file) try { writer.write("ScalaTest is ") // set up the fixture testCode(file, writer) // "loan" the fixture to the test } finally writer.close() // clean up the fixture } "Testing" - { // This test needs the file fixture "should be productive" in withFile { (file, writer) => writer.write("productive!") writer.flush() assert(file.length === 24) } } "Test code" - { // This test needs the database fixture "should be readable" in withDatabase { db => db.append("readable!") assert(db.toString === "ScalaTest is readable!") } // This test needs both the file and the database "should be clear and concise" in withDatabase { db => withFile { (file, writer) => // loan-fixture methods compose db.append("clear!") writer.write("concise!") writer.flush() assert(db.toString === "ScalaTest is clear!") assert(file.length === 21) } } } }As demonstrated by the last test, loan-fixture methods compose. Not only do loan-fixture methods allow you to give each test the fixture it needs, they allow you to give a test multiple fixtures and clean everything up afterwards.
Also demonstrated in this example is the technique of giving each test its own "fixture sandbox" to play in. When your fixtures involve external side-effects, like creating files or databases, it is a good idea to give each file or database a unique name as is done in this example. This keeps tests completely isolated, allowing you to run them in parallel if desired.
Overriding
withFixture(OneArgTest)If all or most tests need the same fixture, you can avoid some of the boilerplate of the loan-fixture method approach by using a
FixtureAnyFreeSpecand overridingwithFixture(OneArgTest). Each test in aFixtureAnyFreeSpectakes a fixture as a parameter, allowing you to pass the fixture into the test. You must indicate the type of the fixture parameter by specifyingFixtureParam, and implement awithFixturemethod that takes aOneArgTest. ThiswithFixturemethod is responsible for invoking the one-arg test function, so you can perform fixture set up before, and clean up after, invoking and passing the fixture into the test function.To enable the stacking of traits that define
withFixture(NoArgTest), it is a good idea to letwithFixture(NoArgTest)invoke the test function instead of invoking the test function directly. To do so, you'll need to convert theOneArgTestto aNoArgTest. You can do that by passing the fixture object to thetoNoArgTestmethod ofOneArgTest. In other words, instead of writing “test(theFixture)”, you'd delegate responsibility for invoking the test function to thewithFixture(NoArgTest)method of the same instance by writing:Here's a complete example:
package org.scalatest.examples.freespec.oneargtest import org.scalatest._ import java.io._ class ExampleSpec extends freespec.FixtureAnyFreeSpec { case class FixtureParam(file: File, writer: FileWriter) def withFixture(test: OneArgTest) = { // create the fixture val file = File.createTempFile("hello", "world") val writer = new FileWriter(file) val theFixture = FixtureParam(file, writer) try { writer.write("ScalaTest is ") // set up the fixture withFixture(test.toNoArgTest(theFixture)) // "loan" the fixture to the test } finally writer.close() // clean up the fixture } "Testing" - { "should be easy" in { f => f.writer.write("easy!") f.writer.flush() assert(f.file.length === 18) } "should be fun" in { f => f.writer.write("fun!") f.writer.flush() assert(f.file.length === 17) } } }In this example, the tests actually required two fixture objects, a
Fileand aFileWriter. In such situations you can simply define theFixtureParamtype to be a tuple containing the objects, or as is done in this example, a case class containing the objects. For more information on thewithFixture(OneArgTest)technique, see the documentation forFixtureAnyFreeSpec.Mixing in
BeforeAndAfterIn all the shared fixture examples shown so far, the activities of creating, setting up, and cleaning up the fixture objects have been performed during the test. This means that if an exception occurs during any of these activities, it will be reported as a test failure. Sometimes, however, you may want setup to happen before the test starts, and cleanup after the test has completed, so that if an exception occurs during setup or cleanup, the entire suite aborts and no more tests are attempted. The simplest way to accomplish this in ScalaTest is to mix in trait
BeforeAndAfter. With this trait you can denote a bit of code to run before each test withbeforeand/or after each test each test withafter, like this:package org.scalatest.examples.freespec.beforeandafter import org.scalatest.freespec.AnyFreeSpec import org.scalatest.BeforeAndAfter import collection.mutable.ListBuffer class ExampleSpec extends AnyFreeSpec with BeforeAndAfter { val builder = new StringBuilder val buffer = new ListBuffer[String] before { builder.append("ScalaTest is ") } after { builder.clear() buffer.clear() } "Testing" - { "should be easy" in { builder.append("easy!") assert(builder.toString === "ScalaTest is easy!") assert(buffer.isEmpty) buffer += "sweet" } "should be fun" in { builder.append("fun!") assert(builder.toString === "ScalaTest is fun!") assert(buffer.isEmpty) } } }Note that the only way
beforeandaftercode can communicate with test code is via some side-effecting mechanism, commonly by reassigning instancevars or by changing the state of mutable objects held from instancevals (as in this example). If using instancevars or mutable objects held from instancevals you wouldn't be able to run tests in parallel in the same instance of the test class (on the JVM, not Scala.js) unless you synchronized access to the shared, mutable state. This is why ScalaTest'sParallelTestExecutiontrait extendsOneInstancePerTest. By running each test in its own instance of the class, each test has its own copy of the instance variables, so you don't need to synchronize. If you mixedParallelTestExecutioninto theExampleSuiteabove, the tests would run in parallel just fine without any synchronization needed on the mutableStringBuilderandListBuffer[String]objects.Although
BeforeAndAfterprovides a minimal-boilerplate way to execute code before and after tests, it isn't designed to enable stackable traits, because the order of execution would be non-obvious. If you want to factor out before and after code that is common to multiple test suites, you should use traitBeforeAndAfterEachinstead, as shown later in the next section, composing fixtures by stacking traits.Composing fixtures by stacking traits
In larger projects, teams often end up with several different fixtures that test classes need in different combinations, and possibly initialized (and cleaned up) in different orders. A good way to accomplish this in ScalaTest is to factor the individual fixtures into traits that can be composed using the stackable trait pattern. This can be done, for example, by placing
withFixturemethods in several traits, each of which callsuper.withFixture. Here's an example in which theStringBuilderandListBuffer[String]fixtures used in the previous examples have been factored out into two stackable fixture traits namedBuilderandBuffer:package org.scalatest.examples.freespec.composingwithfixture import org.scalatest._ import collection.mutable.ListBuffer trait Builder extends TestSuiteMixin { this: TestSuite => val builder = new StringBuilder abstract override def withFixture(test: NoArgTest) = { builder.append("ScalaTest is ") try super.withFixture(test) // To be stackable, must call super.withFixture finally builder.clear() } } trait Buffer extends TestSuiteMixin { this: TestSuite => val buffer = new ListBuffer[String] abstract override def withFixture(test: NoArgTest) = { try super.withFixture(test) // To be stackable, must call super.withFixture finally buffer.clear() } } class ExampleSpec extends freespec.AnyFreeSpec with Builder with Buffer { "Testing" - { "should be easy" in { builder.append("easy!") assert(builder.toString === "ScalaTest is easy!") assert(buffer.isEmpty) buffer += "sweet" } "should be fun" in { builder.append("fun!") assert(builder.toString === "ScalaTest is fun!") assert(buffer.isEmpty) buffer += "clear" } } }By mixing in both the
BuilderandBuffertraits,ExampleSuitegets both fixtures, which will be initialized before each test and cleaned up after. The order the traits are mixed together determines the order of execution. In this case,Builderis “super” toBuffer. If you wantedBufferto be “super” toBuilder, you need only switch the order you mix them together, like this:And if you only need one fixture you mix in only that trait:
Another way to create stackable fixture traits is by extending the
BeforeAndAfterEachand/orBeforeAndAfterAlltraits.BeforeAndAfterEachhas abeforeEachmethod that will be run before each test (like JUnit'ssetUp), and anafterEachmethod that will be run after (like JUnit'stearDown). Similarly,BeforeAndAfterAllhas abeforeAllmethod that will be run before all tests, and anafterAllmethod that will be run after all tests. Here's what the previously shown example would look like if it were rewritten to use theBeforeAndAfterEachmethods instead ofwithFixture:package org.scalatest.examples.freespec.composingbeforeandaftereach import org.scalatest._ import org.scalatest.BeforeAndAfterEach import collection.mutable.ListBuffer trait Builder extends BeforeAndAfterEach { this: Suite => val builder = new StringBuilder override def beforeEach() { builder.append("ScalaTest is ") super.beforeEach() // To be stackable, must call super.beforeEach } override def afterEach() { try super.afterEach() // To be stackable, must call super.afterEach finally builder.clear() } } trait Buffer extends BeforeAndAfterEach { this: Suite => val buffer = new ListBuffer[String] override def afterEach() { try super.afterEach() // To be stackable, must call super.afterEach finally buffer.clear() } } class ExampleSpec extends freespec.AnyFreeSpec with Builder with Buffer { "Testing" - { "should be easy" in { builder.append("easy!") assert(builder.toString === "ScalaTest is easy!") assert(buffer.isEmpty) buffer += "sweet" } "should be fun" in { builder.append("fun!") assert(builder.toString === "ScalaTest is fun!") assert(buffer.isEmpty) buffer += "clear" } } }To get the same ordering as
withFixture, place yoursuper.beforeEachcall at the end of eachbeforeEachmethod, and thesuper.afterEachcall at the beginning of eachafterEachmethod, as shown in the previous example. It is a good idea to invokesuper.afterEachin atryblock and perform cleanup in afinallyclause, as shown in the previous example, because this ensures the cleanup code is performed even ifsuper.afterEachthrows an exception.The difference between stacking traits that extend
BeforeAndAfterEachversus traits that implementwithFixtureis that setup and cleanup code happens before and after the test inBeforeAndAfterEach, but at the beginning and end of the test inwithFixture. Thus if awithFixturemethod completes abruptly with an exception, it is considered a failed test. By contrast, if any of thebeforeEachorafterEachmethods ofBeforeAndAfterEachcomplete abruptly, it is considered an aborted suite, which will result in aSuiteAbortedevent.Shared tests
Sometimes you may want to run the same test code on different fixture objects. In other words, you may want to write tests that are "shared" by different fixture objects. To accomplish this in a
AnyFreeSpec, you first place shared tests in behavior functions. These behavior functions will be invoked during the construction phase of anyAnyFreeSpecthat uses them, so that the tests they contain will be registered as tests in thatAnyFreeSpec. For example, given this stack class:import scala.collection.mutable.ListBuffer class Stack[T] { val MAX = 10 private val buf = new ListBuffer[T] def push(o: T) { if (!full) buf.prepend(o) else throw new IllegalStateException("can't push onto a full stack") } def pop(): T = { if (!empty) buf.remove(0) else throw new IllegalStateException("can't pop an empty stack") } def peek: T = { if (!empty) buf(0) else throw new IllegalStateException("can't pop an empty stack") } def full: Boolean = buf.size == MAX def empty: Boolean = buf.size == 0 def size = buf.size override def toString = buf.mkString("Stack(", ", ", ")") }You may want to test the
Stackclass in different states: empty, full, with one item, with one item less than capacity, etc. You may find you have several tests that make sense any time the stack is non-empty. Thus you'd ideally want to run those same tests for three stack fixture objects: a full stack, a stack with a one item, and a stack with one item less than capacity. With shared tests, you can factor these tests out into a behavior function, into which you pass the stack fixture to use when running the tests. So in yourAnyFreeSpecfor stack, you'd invoke the behavior function three times, passing in each of the three stack fixtures so that the shared tests are run for all three fixtures. You can define a behavior function that encapsulates these shared tests inside theAnyFreeSpecthat uses them. If they are shared between differentAnyFreeSpecs, however, you could also define them in a separate trait that is mixed into eachAnyFreeSpecthat uses them.For example, here the
nonEmptyStackbehavior function (in this case, a behavior method) is defined in a trait along with another method containing shared tests for non-full stacks:trait StackBehaviors { this: AnyFreeSpec => def nonEmptyStack(newStack: => Stack[Int], lastItemAdded: Int) { "be non-empty" in { assert(!newStack.empty) } "return the top item on peek" in { assert(newStack.peek === lastItemAdded) } "not remove the top item on peek" in { val stack = newStack val size = stack.size assert(stack.peek === lastItemAdded) assert(stack.size === size) } "remove the top item on pop" in { val stack = newStack val size = stack.size assert(stack.pop === lastItemAdded) assert(stack.size === size - 1) } } def nonFullStack(newStack: => Stack[Int]) { "not be full" in { assert(!newStack.full) } "add to the top on push" in { val stack = newStack val size = stack.size stack.push(7) assert(stack.size === size + 1) assert(stack.peek === 7) } } }Given these behavior functions, you could invoke them directly, but
AnyFreeSpecoffers a DSL for the purpose, which looks like this:If you prefer to use an imperative style to change fixtures, for example by mixing in
BeforeAndAfterEachand reassigning astackvarinbeforeEach, you could write your behavior functions in the context of thatvar, which means you wouldn't need to pass in the stack fixture because it would be in scope already inside the behavior function. In that case, your code would look like this:The recommended style, however, is the functional, pass-all-the-needed-values-in style. Here's an example:
class SharedTestExampleSpec extends AnyFreeSpec with StackBehaviors { // Stack fixture creation methods def emptyStack = new Stack[Int] def fullStack = { val stack = new Stack[Int] for (i <- 0 until stack.MAX) stack.push(i) stack } def stackWithOneItem = { val stack = new Stack[Int] stack.push(9) stack } def stackWithOneItemLessThanCapacity = { val stack = new Stack[Int] for (i <- 1 to 9) stack.push(i) stack } val lastValuePushed = 9 "A Stack" - { "when empty" - { "should be empty" in { assert(emptyStack.empty) } "should complain on peek" in { assertThrows[IllegalStateException] { emptyStack.peek } } "should complain on pop" in { assertThrows[IllegalStateException] { emptyStack.pop } } } "when it contains one item" - { "should" - { behave like nonEmptyStack(stackWithOneItem, lastValuePushed) behave like nonFullStack(stackWithOneItem) } } "when it contains one item less than capacity" - { "should" - { behave like nonEmptyStack(stackWithOneItemLessThanCapacity, lastValuePushed) behave like nonFullStack(stackWithOneItemLessThanCapacity) } } "when full" - { "should be full" in { assert(fullStack.full) } "should" - { behave like nonEmptyStack(fullStack, lastValuePushed) } "should complain on a push" in { assertThrows[IllegalStateException] { fullStack.push(10) } } } } }If you load these classes into the Scala interpreter (with scalatest's JAR file on the class path), and execute it, you'll see:
scala> org.scalatest.run(new SharedTestExampleSpec) SharedTestExampleSpec: A Stack when empty - should be empty - should complain on peek - should complain on pop when it contains one item should - be non-empty - return the top item on peek - not remove the top item on peek - remove the top item on pop - not be full - add to the top on push when it contains one item less than capacity should - be non-empty - return the top item on peek - not remove the top item on peek - remove the top item on pop - not be full - add to the top on push when full - should be full should - be non-empty - return the top item on peek - not remove the top item on peek - remove the top item on pop - should complain on a pushOne thing to keep in mind when using shared tests is that in ScalaTest, each test in a suite must have a unique name. If you register the same tests repeatedly in the same suite, one problem you may encounter is an exception at runtime complaining that multiple tests are being registered with the same test name. A good way to solve this problem in a
AnyFreeSpecis to make sure each test is in the context of different surrounding description clauses, because a test's name is the concatenation of its surrounding clauses, followed by the test's text. For example, the following code in aAnyFreeSpecwould register a test with the name"A Stack when empty should be empty":"A Stack" - { "when empty" - { "should be empty" in { assert(emptyStack.empty) } } } // ...If the
"should be empty"test was factored out into a behavior function, it could be called repeatedly so long as each invocation of the behavior function is in the context of a different surrounding description (dash) clauses.