Part 1 – What is Mockito?
In this tutorial, we will understand below topics –
– What is a Mock Object?
– When should I mock?
– Mockito Framework
– Enable Mockito Annotations
– How to Mock Object with @Mock & @InjectMock annotations in Spring application?
https://www.onlyfullstack.com/what-is-mock-object-what-is-mockito/
1. when/then
2. when/thenThrow
3. when/thenAnswer
https://www.onlyfullstack.com/how-to-mock-methods-with-mockito/
– Mocking Void Methods
– Three ways to mock the void method:
1. doNothing/when
2. doAnswer/when
3. doThrow/when
https://www.onlyfullstack.com/how-to-mock-void-methods-with-mockito/
– Simple verify method
– Variations in verify method
– Verify with the number of times
– Mockito Verify Order of Invocation
https://www.onlyfullstack.com/how-to-verify-the-mocks-in-mockito/
Mockito Mock vs Spy
1. Object declaration –
Mock – We don’t need to instantiate the mock List as the @Mock will create and instantiate the list for us.
Spy- We need to instantiate the list object as the @Spy will use the real object’s method if we don’t mock them.
/* We dont need to instantiate the mock List as the @Mock will create and instantiate the list for us */ @Mock private List<String> mockedList; /* We need to instantiate the list object as the @Spy will use the real objects method if we dont mock them */ @Spy private List<String> spyList = new ArrayList();
2. When the methods are not mocked –
Mock – If we don’t mock the methods of @Mock object and try to call them then it will not do anything.
Spy – add method is not mocked so the spyList will execute the default behaviour of the add method and it will add a new String into the list.
@RunWith(MockitoJUnitRunner.class) public final class MockVsSpy { /* We dont need to instantiate the mock List as the @Mock will create and instantiate the list for us */ @Mock private List<String> mockedList; /* We need to instantiate the list object as the @Spy will use the real objects method if we dont mock them */ @Spy private List<String> spyList = new ArrayList(); @Test public void testMockList_checkDefaultBehaviour_whenMethodIsNotMocked() { /*If we dont mock the methods of @Mock object and try to call them then it will not do anything.*/ mockedList.add("test"); // add the String into list which will not do anything assertNull(mockedList.get(0)); // As the String was not added into the list it will return null value } @Test public void testSpyList_checkDefaultBehaviour_whenMethodIsNotMocked() { /* add method is not mocked so the spyList will execute * the default behaviour of the add method and it will add a new String into list*/ spyList.add("test"); assertEquals("test", spyList.get(0)); } }
3. When the method is mocked –
Mock – Mock will execute as per the above example and it will not add or get the element from the mockedList.
Spy – add method is not mocked so the spyList will execute the default behaviour of the add method and it will add a new String into the list.
@Test public void testMockList_whenMethodIsMocked() { /*If we dont mock the methods of @Mock object and try to call them then it will not do anything.*/ when(mockedList.size()).thenReturn(10); mockedList.add("One"); assertNull(mockedList.get(0)); // Again the execution of add and get methods will not have any impact on mocked object assertEquals(10, mockedList.size()); // As the String was not added into the list it will return null value } @Test public void testSpyList_whenMethodIsMocked() { /* add method is not mocked so the spyList will execute * the default behaviour of the add method and it will add a new String into list*/ when(spyList.size()).thenReturn(10); spyList.add("One"); assertEquals("One", spyList.get(0)); assertEquals(10, spyList.size()); // size method will return 10 as we have mocked its implementation }
Source Code
Download the source code of JUnit tutorial from below git repository :
unit-testing-and-integration-testing-with-spring-boot
Mockito Tutorial
https://www.onlyfullstack.com/mockito-tutorial/
