／var／logmarcus chiu

Java - Mockito - ArgumentMatcher - AdditionalMatcher - Custom ArgumentMatcher

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2 Ways in Configuring Mocked Methods

Fixed Values
doReturn("Flower").when(flowerService).analyze("poppy");
ArgumentMatchers
when(flowerService.analyze(anyString())).thenReturn("Flower");

ArgumentMatchers - Restrictions

Mockito requires ALL provided arguments to be: ArgumentMatchers or Exact Values
when(mock.isABigFlower("poppy", anyInt())).thenReturn(true); <-- BAD
when(mock.isABigFlower(eq("poppy"), anyInt())).thenReturn(true); <-- GOOD using eq() ArgumentMatcher

Here are two more points to take care when ArgumentMatchers are used:

  • we can’t use ArgumentMatchers outside of verification or stubbing
  • we can’t use them as a return value, an exact value is required when stubbing calls

AdditionalMatchers - not() and() or()

Mockito also provides AdditionalMatchers to implement common logical operations (‘not’, ‘and’, ‘or’) on ArgumentMatchers that match both primitive and non-primitive types:

verify(mock).analyze(or(eq("poppy"), endsWith("y")));

Custom ArgumentMatcher

Problem
verify(messageService, times(1)).deliverMessage(any(Message.class));

This approach doesn’t let us validate the data inside the Message

Solution

Implement a custom ArgumentMatcher

public class MessageMatcher implements ArgumentMatcher<Message> {

    private Message left;

    // constructors

    @Override
    public boolean matches(Message right) {
        return left.getFrom().equals(right.getFrom()) &&
          left.getTo().equals(right.getTo()) &&
          left.getText().equals(right.getText()) &&
          right.getDate() != null &&
          right.getId() != null;
    }
}

verify(messageService, times(1)).deliverMessage(argThat(new MessageMatcher(message)));

Custom ArgumentMatcher vs ArgumentCaptor

see: Java - Mockito - ArgumentCaptor vs Custom ArgumentMatcher