该系列文章翻译自https://www.baeldung.com/mockito-series

1.最简单的mock方法

public static <T> T mock(Class<T> classToMock)

举例如下：

@Test
    public void whenUsingSimpleMock_thenCorrect() {
        MyList listMock = mock(MyList.class);
        when(listMock.add(anyString())).thenReturn(false);
        boolean added = listMock.add(randomAlphabetic(6));

        verify(listMock).add(anyString());
        assertThat(added, is(false));
    }

2.设置mock对象的名称

public static <T> T mock(Class<T> classToMock, String name)

举例如下：

    @Rule
    public ExpectedException thrown = ExpectedException.none();

    @Test
    public void whenUsingMockWithName_thenCorrect() {
        MyList listMock = mock(MyList.class, "myMock");
        when(listMock.add(anyString())).thenReturn(false);
        listMock.add(randomAlphabetic(6));
        
        thrown.expect(TooLittleActualInvocations.class);
        thrown.expectMessage(containsString("myMock.add"));

        verify(listMock, times(2)).add(anyString());
    }

其中，listMock只做了一次add操作，因此，verify(listMock, times(2)).add(anyString())会抛出TooLittleActualInvocations类型的错误，可以看到，在错误详情中显示的mock对象名称，就是我们在创建mock对象时指定的值myMock.

org.mockito.exceptions.verification.TooLittleActualInvocations:
myMock.add(<any>);
Wanted 2 times:
at com.baeldung.mockito.MockitoMockTest
  .whenUsingMockWithName_thenCorrect(MockitoMockTest.java:...)
but was 1 time:
at com.baeldung.mockito.MockitoMockTest
  .whenUsingMockWithName_thenCorrect(MockitoMockTest.java:...)

3.设置mock对象的默认返回

在创建mock对象时，可以指定默认返回。如下例：创建mock对象时，指定默认返回为false.

    private static class CustomAnswer implements Answer<Boolean> {
        @Override
        public Boolean answer(InvocationOnMock invocation) throws Throwable {
            return false;
        }
    }

    @Test
    public void whenUsingMockWithAnswer_thenCorrect() {
        MyList listMock = mock(MyList.class, new CustomAnswer());
        boolean added = listMock.add(randomAlphabetic(6));

        verify(listMock).add(anyString());
        assertThat(added, is(false));
    }

4.自定义属性

MockSettings接口支持自定义的设置，比如下例中，通过defaultAnswer自定义一个默认返回

    private static class CustomAnswer implements Answer<Boolean> {
        @Override
        public Boolean answer(InvocationOnMock invocation) throws Throwable {
            return false;
        }
    }

    @Test
    public void whenUsingMockWithSettings_thenCorrect() {
        MockSettings customSettings = withSettings().defaultAnswer(new CustomAnswer());
        MyList listMock = mock(MyList.class, customSettings);
        boolean added = listMock.add(randomAlphabetic(6));

        verify(listMock).add(anyString());
        assertThat(added, is(false));
    }