org.mockito

Class ArgumentMatcher<T>

java.lang.Object

org.hamcrest.BaseMatcher<T>

org.mockito.ArgumentMatcher<T>

Type Parameters:

T - type of argument

All Implemented Interfaces:

org.hamcrest.Matcher<T>, org.hamcrest.SelfDescribing

Direct Known Subclasses:

And, Any, AnyVararg, CapturingMatcher, CompareTo, Contains, EndsWith, Equals, EqualsWithDelta, Find, InstanceOf, Matches, Not, NotNull, Null, Or, ReflectionEquals, Same, StartsWith, VarargCapturingMatcher

public abstract class ArgumentMatcher<T>
extends org.hamcrest.BaseMatcher<T>

Allows creating customized argument matchers.

ArgumentMatcher is an hamcrest Matcher with predefined describeTo() method. In case of failure, ArgumentMatcher generates description based on decamelized class name - to promote meaningful class names. For example StringWithStrongLanguage matcher will generate 'String with strong language' description. You can always override describeTo() method and provide detailed description.

Use Matchers.argThat(org.hamcrest.Matcher<T>) method and pass an instance of hamcrest Matcher, e.g:

 class IsListOfTwoElements extends ArgumentMatcher<List> {
     public boolean matches(Object list) {
         return ((List) list).size() == 2;
     }
 }
 
 List mock = mock(List.class);
 
 when(mock.addAll(argThat(new IsListOfTwoElements()))).thenReturn(true);
 
 mock.addAll(Arrays.asList("one", "two"));
 
 verify(mock).addAll(argThat(new IsListOfTwoElements()));
 

To keep it readable you may want to extract method, e.g:

   verify(mock).addAll(argThat(new IsListOfTwoElements()));
   //becomes
   verify(mock).addAll(listOfTwoElements());
 

Warning: Be reasonable with using complicated argument matching, especially custom argument matchers, as it can make the test less readable. Sometimes it's better to implement equals() for arguments that are passed to mocks (Mockito naturally uses equals() for argument matching). This can make the test cleaner.

Also, sometimes ArgumentCaptor may be a better fit than custom matcher. For example, if custom argument matcher is not likely to be reused or you just need it to assert on argument values to complete verification of behavior.

Read more about other matchers in javadoc for Matchers class

Constructor Summary

Constructors

Constructor and Description
ArgumentMatcher()

Method Summary

Methods

Modifier and Type	Method and Description
void	describeTo(org.hamcrest.Description description) By default this method decamelizes matchers name to promote meaningful names for matchers.
abstract boolean	matches(java.lang.Object argument) Returns whether this matcher accepts the given argument.

Methods inherited from class org.hamcrest.BaseMatcher

_dont_implement_Matcher___instead_extend_BaseMatcher_, toString

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail

ArgumentMatcher

public ArgumentMatcher()

Method Detail

matches

public abstract boolean matches(java.lang.Object argument)

Returns whether this matcher accepts the given argument.

The method should never assert if the argument doesn't match. It should only return false.

Parameters:

argument - the argument

Returns:

whether this matcher accepts the given argument.

describeTo

public void describeTo(org.hamcrest.Description description)

By default this method decamelizes matchers name to promote meaningful names for matchers.

For example StringWithStrongLanguage matcher will generate 'String with strong language' description in case of failure.

You might want to override this method to provide more specific description of the matcher (useful when verification failures are reported).

Parameters:

description - the description to which the matcher description is appended.