Package org.saynotobugs.confidence.quality.function

Class MutatesArgument<Argument,​Type>

  • All Implemented Interfaces:
    Quality<java.util.function.Function<Argument,​Type>>
    public final class MutatesArgument<Argument,​Type>
extends java.lang.Object
implements Quality<java.util.function.Function<Argument,​Type>>
    Quality of a non-pure Function that mutates its argument when called.

    Examples

    The following test ensures the function list->list:add adds an element to a given List and returns true when the list content has been changed. 

    
 assertThat(list -> list::add,
     mutatesArgument(
         ArrayList::new,
         soIt(iterates("a")),
         when(maps("a", to(true)))));

    A common use case is testing mutation of Constructor arguments of mutable classes. Consider a ListAppender Consumer that appends any value to the given list. 

    
 assertThat(list -> new ListAppender(list),
     mutatesArgument(
         ArrayList::new,
         soIt(iterates("a")),
         when(consumerThatAccepts("a"))));