Mockito 与春天

Question

For one of my use case, I have to mock an autowired dependency only a single test case, while I want other tests to use the original one.

public class A {

    @Autowired
    private B b;
}

Class TestA {

    @Autowired
    private A a;

    void test1() {
    //using B without mock.
    }

    void test2() {
    // mock B b in A here
    }
}

I want to mock the private class variable 'b' here in some particular tests. I know if I have to mock B in entire class I can use @Mock, @InjectMocks and MockitoAnnotations.initMocks(), but that will mock 'b' for the other test cases as well where I want original behavior.

Answer 1

You can simply create a mock object, and temporarily assign it to variable b . Something like

public void test1() {
   //normal test
}

while in the other:

public void test2() {
   try {
      B autowiredObject = b; //saving the original reference
      b = mock(B.class);
      when(b.someGetFunction()).thenReturn("it is mocked");
      //rest of your test
   } finally {
      b = autowiredObject;
   }
}

Please note the finally clause. It is there to ensure that the class state (autowired dependency) gets restored during your test. This is a very important practice, otherwise a fail in your test could theorertically affect your other tests in the same class, which is something you should always avoid.

Answer 2

Usually, you don't use Spring for unit-testing but rely on mocking dependencies and inject them manually into the test-object. A simple test method therefore can look like this:

@Test
public void testSomethingWithA() throws Exception {
    // Arrange
    A sut = new A();
    B mockedB = mock(B.class);

    // inject B into A
    Whitebox.setInternalState(sut, "b", mockedB);

    // Act
    Object retVal = sut.doSomething();

    // Assert
    assertThat(retVal, is(equalTo(someExpectedValue)));
}

If you want to inject a real object into A instead of a mocked object (for whatever reason) simply switch mockedB in Whitebox.setInternalState(...) with your real object.