在Mockito中捕捉一个论点

Question

我正在测试某个班级.该类在内部实例化一个"GetMethod"对象,该对象被传递给"HttpClient"对象,该对象被注入到测试类中.

我正在嘲笑"HttpClient"类,但我还需要修改"GetMethod"类的一个方法的行为.我正在玩ArgumentCaptor,但我似乎无法在"when"调用中获取实例化对象.

例:

HttpClient mockHttpClient = mock(HttpClient.class);
ArgumentCaptor<GetMethod> getMethod = ArgumentCaptor.forClass(GetMethod.class);
when(mockHttpClient.executeMethod(getMethod.capture())).thenReturn(HttpStatus.SC_OK);
when(getMethod.getValue().getResponseBodyAsStream()).thenReturn(new FileInputStream(source));

响应:

org.mockito.exceptions.base.MockitoException: 
No argument value was captured!
You might have forgotten to use argument.capture() in verify()...
...or you used capture() in stubbing but stubbed method was not called.
Be aware that it is recommended to use capture() only with verify()

Answer 1

你不能when在getMethod上使用,因为getMethod不是mock.它仍然是您的班级创建的真实对象.

ArgumentCaptor有着截然不同的目的.在这里查看第15节.

您可以使您的代码更易于测试.通常,创建其他类的新实例的类很难测试.把一些工厂放到这个类来创建get/post方法,然后在test mock中修改这个工厂,并使它成为模拟get/post方法.

public class YourClass {
  MethodFactory mf;

  public YourClass(MethodFactory mf) {
    this.mf = mf;
  }

  public void handleHttpClient(HttpClient httpClient) {
    httpClient.executeMethod(mf.createMethod());
    //your code here
  }
}

然后在测试中你可以做到:

HttpClient mockHttpClient = mock(HttpClient.class);
when(mockHttpClient.executeMethod(any(GetMethod.class)).thenReturn(HttpStatus.SC_OK);

MethodFactory factory = mock(MethodFactory.class);
GetMethod get = mock(GetMethod.class);
when(factory.createMethod()).thenReturn(get);
when(get.getResponseBodyAsStream()).thenReturn(new FileInputStream(source));

UPDATE

您还可以尝试一些讨厌的黑客,并Answer通过反射访问GetMethod的私有部分;).(这真是讨厌的黑客)

when(mockHttpClient.executeMethod(any(GetMethod.class))).thenAnswer(new Answer() {
  Object answer(InvocationOnMock invocation) {
    GetMethod getMethod = (GetMethod) invocation.getArguments()[0];

    Field respStream = HttpMethodBase.class.getDeclaredField("responseStream");
    respStream.setAccessible(true);
    respStream.set(getMethod, new FileInputStream(source));

    return HttpStatus.SC_OK;
  }
});

Answer 2

好的，我就是这样解决的。有点复杂，但找不到其他方法。

在测试类中：

private GetMethod getMethod;

public void testMethod() {
    when(mockHttpClient.executeMethod(any(GetMethod.class))).thenAnswer(new ExecuteMethodAnswer());
    //Execute your tested method here.
    //Acces the getMethod here, assert stuff against it.  
}

private void setResponseStream(HttpMethodBase httpMethod, InputStream inputStream) throws NoSuchFieldException, IllegalAccessException {
    Field privateResponseStream = HttpMethodBase.class.getDeclaredField("responseStream");
    privateResponseStream.setAccessible(true);
    privateResponseStream.set(httpMethod, inputStream);
}

private class ExecuteMethodAnswer implements Answer {
    public Object answer(InvocationOnMock invocation) throws FileNotFoundException,
                                                             NoSuchFieldException, IllegalAccessException {
        getMethod = (GetMethod) invocation.getArguments()[0];
        setResponseStream(getMethod, new FileInputStream(source));
        return HttpStatus.SC_OK;
    }
}