Mockito intro
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This document defines and describes various types of test doubles (dummy objects, fakes, stubs, mocks, spies) that are used for testing purposes. It provides examples of how to create mocks using Mockito, stub behaviors for mocks, verify interactions with mocks, and some limitations of mocking with Mockito.
Mockito intro
- 1. Cristian R. Silva about.me/ocristian
- 2. Test Doubles generic term for any kind of pretend object used in place of a real object for testing purposes 2
- 3. Dummy Object objects are passed around but never actually used. Usually they are just used to fill parameter lists 3
- 4. Fake Object objects actually have working implementations, but usually take some shortcut which makes them not suitable for production (an in memory database is a good example). 4
- 5. provide canned answers to calls made during the test, usually not responding at all to anything outside what's programmed in for the test. Stubs may also record information about calls, such as an email gateway stub that remembers the messages it 'sent', or maybe only how many messages it 'sent' Stub 5
- 6. an object with the ability to have a programmed expected behavior, and verify the interactions occurring in its lifetime (this object is usually created with the help of mocking framework) Mock 6
- 7. a mock created as a proxy to an existing real object; some methods can be stubbed, while the un- stubbed ones are for- warded to the covered object Spy 7
- 9. creating mock objects import org.mockito.Mockito; Person person = Mockito.mock(Person.class); or import static org.mockito.Mockito.mock; Person person = mock(Person.class); 9 using static method mock()
- 10. creating mock objects 10 using @Mock annotation @RunWith(MockitoJUnitRunner.class) public class ClassTest { } or public class ClassTest{ MockitoAnnotations.initMocks(ClassTest.class); }
- 11. creating mock objects declaring an attribute with the @Mock annotation public class ClassTest { @Mock private Person person; 11 }
- 12. requesting specific behaviors Method Description thenReturn(T valueToBeReturned) returns given value thenThrow(Throwable toBeThrown) thenThrow(Class<? extends Throwable> toBeThrown) 12 throws given exception then(Answer answer) thenAnswer(Answer answer) uses user created code to answer thenCallRealMethod() calls real method when working with partial mock/spy
- 13. stubbing method public class SimpleStubbingTest { public static final int TEST_NUMBER_OF_RELATIVES = 5; @Test public void shouldReturnGivenValue() { Person person = mock(Person.class); when(person.getNumberOfRelatives()) .thenReturn(TEST_NUMBER_OF_RELATIVES); int numberOfRelatives = person.getNumberOfRelatives(); assertEquals(numberOfRelatives, TEST_NUMBER_OF_RELATIVES); 13 } }
- 14. BDDMockito given - when - then @Test public void shouldReturnGivenValueUsingBDDSemantics() { // given Person person = mock(Person.class); given(person.getNumberOfRelatives()).willReturn( TEST_NUMBER_OF_RELATIVES); // when int numberOfRelatives = person.getNumberOfRelatives(); // then assertEquals(numberOfRelatives, TEST_NUMBER_OF_RELATIVES); 14 }
- 15. stubbing multiples calls to the same method @Test public void shouldReturnLastDefinedValue() { Weather weather = mock(Weather.class); given(weather.getTemperature()).willReturn( 10, 12, 23 ); assertEquals(weather.getTemperature(), 10); assertEquals(weather.getTemperature(), 12); assertEquals(weather.getTemperature(), 23); assertEquals(weather.getTemperature(), 23); 15 }
- 16. stubbing void methods @Test(expected = WeatherException.class) public void shouldStubVoidMethod() { Weather weather = mock(Weather.class); doThrow(WeatherException.class).when(weather).doSelfCheck(); //exception expected weather.doSelfCheck(); 16 }
- 17. custom answer public class ReturnCustomAnswer implements Answer<Object> { public Object answer(InvocationOnMock invocation) 17 throws Throwable { return null; } }
- 18. verifying behavior Method Description times(int wantedNumberOfInvocations) called exactly n times (one by default) never() never called atLeastOnce() called at least once atLeast(int minNumberOfInvocations) called at least n times atMost(int maxNumberOfInvocations) called at most n times only() the only method called on a mock timeout(int millis) interacted in a specified time range 18
- 19. verifying behavior verify(mockObject, never()).doSelfCheck(); verify(mockObject, times(2)).getNumberOfRelatives(); verify(mockObject, atLeast(1)).getTemperature(); 19
- 20. another verifications InOrder API verifying the call order ArgumentCaptor argument matching timeout verify(mockObject, timeout(10)).getTemperature(); 20
- 21. some limitations • mock final classes • mock enums • mock final methods • mock static methods • mock private methods • mock hashCode() and equals() 21 https://code.google.com/p/powermock/ will help you!
- 22. references 22 https://code.google.com/p/mockito/ http://martinfowler.com/articles/mocksArentStubs.html blog.caelum.com.br/facilitando-seus-testes-de-unidade-no-java-um-pouco-de-mockito/ http://refcardz.dzone.com/refcardz/mockito
- 23. ? 23