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Mockito is a mocking framework for unit tests in Java. It has been designed to be intuitive to use when the test needs mocks.

• Simple usage : stub, use, verify
• Programatic creation of mocks via mock() or spy()
• Programmatic stubbing via
  • Mockito.when(mock.action()).thenReturn(true)
  • BDDMOckito.given(mock.action()).willReturn(true)
• Customize mock answer or provide your own
• Programmatic verification via
  • Mockito.verify(mock).action()
  • BDDMockito.then(mock).should().action()
• Annotation sugar via @Mock, @Spy, @Captor or @InjectMocks
• JUnit first class support via the runner MockitoJUnitRunner and the now favored rule MockitoJUnit.rule()

Remember

• Do not mock types you don't own
• Don't mock value objects
• Don't mock everything
• Show some love with your tests

Examples

// You can mock concrete classes and interfaces
TrainSeats seats = mock(TrainSeats.class);

// stubbing appears before the actual execution
when(seats.book(Seat.near(WINDOW).in(FIRST_CLASS))).thenReturn(BOOKED);

// the following prints "BOOKED"
System.out.println(seats.book(Seat.near(WINDOW).in(FIRST_CLASS)));

// the following prints "null" because 
// .book(Seat.near(AISLE).in(FIRST_CLASS))) was not stubbed
System.out.println(seats.book(Seat.near(AISLE).in(FIRST_CLASS)));

// the following verification passes because 
// .book(Seat.near(WINDOW).in(FIRST_CLASS)) has been invoked
verify(seats).book(Seat.near(WINDOW).in(FIRST_CLASS))

// the following verification fails because 
// .book(Seat.in(SECOND_CLASS)) has not been invoked
verify(seats).book(Seat.in(SECOND_CLASS))

The BDD way :

// You can mock concrete classes and interfaces
TrainSeats seats = mock(TrainSeats.class);

// stubbing appears before the actual execution
given(seats.book(Seat.near(WINDOW).in(FIRST_CLASS))).willReturn(BOOKED);

// the following prints "BOOKED"
System.out.println(seats.book(Seat.near(WINDOW).in(FIRST_CLASS)));

// the following prints "null" because 
// .book(Seat.near(AISLE).in(FIRST_CLASS))) was not stubbed
System.out.println(seats.book(Seat.near(AISLE).in(FIRST_CLASS)));

// the following verification passes because 
// .book(Seat.near(WINDOW).in(FIRST_CLASS)) has been invoked
then(seats).should().book(Seat.near(WINDOW).in(FIRST_CLASS))

// the following verification fails because 
// .book(Seat.in(SECOND_CLASS)) has not been invoked
then(seats).should().book(Seat.in(SECOND_CLASS))

More

• The very latest javadoc
• Release Notes
• If you have questions, please read our FAQ
• [Read the features and motivation](Features And Motivations)
• Want to contribute, read this
• License
• Related Projects