java - 模拟: doAnswer Vs thenReturn

Question

我正在使用 Mockito 进行后期单元测试。我对何时使用 doAnswer 和 thenReturn 感到困惑。

谁能帮我详细介绍一下？到目前为止，我已经用 thenReturn 进行了尝试。

Answer 1

如果在模拟方法调用时知道返回值，则应使用 thenReturn 或 doReturn。调用模拟方法时会返回此定义的值。

thenReturn(T value) Sets a return value to be returned when the method is called.

@Test
public void test_return() throws Exception {
    Dummy dummy = mock(Dummy.class);
    int returnValue = 5;

    // choose your preferred way
    when(dummy.stringLength("dummy")).thenReturn(returnValue);
    doReturn(returnValue).when(dummy).stringLength("dummy");
}

Answer 用于在调用模拟方法时需要执行其他操作，例如当需要根据该方法调用的参数计算返回值时。

Use doAnswer() when you want to stub a void method with generic Answer.

Answer specifies an action that is executed and a return value that is returned when you interact with the mock.

@Test
public void test_answer() throws Exception {
    Dummy dummy = mock(Dummy.class);
    Answer<Integer> answer = new Answer<Integer>() {
        public Integer answer(InvocationOnMock invocation) throws Throwable {
            String string = invocation.getArgumentAt(0, String.class);
            return string.length() * 2;
        }
    };

    // choose your preferred way
    when(dummy.stringLength("dummy")).thenAnswer(answer);
    doAnswer(answer).when(dummy).stringLength("dummy");
}