Mockito模拟所有方法调用并返回

Question

I have a problem when writing unit testing with mock. There is a object which I need to mock have a lot getter, which I do call them at the code. However, those are not the purpose of my unit test. So, is there is a way I can mock all the methods instead of mock them one by one.

Here is the code example:

public class ObjectNeedToMock{

private String field1;
...
private String field20;

private int theImportantInt;


public String getField1(){return this.field1;}
...

public String getField20(){return this.field20;}

public int getTheImportantInt(){return this.theImportantInt;}

}

and this is the service class I need to test

public class Service{

public void methodNeedToTest(ObjectNeedToMock objectNeedToMock){
    String stringThatIdontCare1 = objectNeedToMock.getField1();
    ...
    String stringThatIdontCare20 = objectNeedToMock.getField20();
    // do something with the field1 to field20

    int veryImportantInt = objectNeedToMock.getTheImportantInt();
    // do something with the veryImportantInt

    }
}

within the test class, the test method is like

@Test
public void testMethodNeedToTest() throws Exception {
      ObjectNeedToMock o = mock(ObjectNeedToMock.class);
      when(o.getField1()).thenReturn(anyString());
      ....
      when(o.getField20()).thenReturn(anyString());

      when(o.getTheImportantInt()).thenReturn("1"); //This "1" is the only thing I care

}

So, is there a way that I can avoid writing all the "when" for the useless "field1" to "field20"

Answer 1

You can control the default answers of your mock. When you're creating the mock, use:

Mockito.mock(ObjectNeedToMock.class, new Answer() {
    @Override
    public Object answer(InvocationOnMock invocation) throws Throwable {
        /* 
           Put your default answer logic here.
           It should be based on type of arguments you consume and the type of arguments you return.
           i.e.
        */
        if (String.class.equals(invocation.getMethod().getReturnType())) {
            return "This is my default answer for all methods that returns string";
        } else {
            return RETURNS_DEFAULTS.answer(invocation);
        }
    }
}));

Answer 2

If you're not interested in the result of getField1() to getField20() in a particular test case, you shouldn't mock it at all. In other words, if all the specific test case should be concerned about is getTheImportantInt() , then your test case should look like this:

@Test
public void testMethodNeedToTest() throws Exception {
      ObjectNeedToMock o = mock(ObjectNeedToMock.class);
      when(o.getTheImportantInt()).thenReturn("1");

      // test code goes here
}

Answer 3

For kotlin users:

val mocked:MyClassToMock = Mockito.mock(MyClassToMock::class.java,
                object:Answer<Any> {

            override fun answer(invocation: InvocationOnMock?): Any {
                    if (String::class.java.equals (invocation?.method?.getReturnType())) {
                        return "Default answer for all methods that returns string";
                    } else {
                        return Mockito.RETURNS_DEFAULTS.answer(invocation);
                    }
            }
        })