测试根据输入调用内部方法的公共方法

Question

So we have this method here that is accessible by the rest of the system which calls underlying methods according to the input.

public SomeReturnObj doSomethingWithInputs(List<Input> inputs) {
  for(Input input : inputs) {
    if(input.getName().equals("A") {
        handleAInput(input);
    }
    else if(input.getName().equals("B") {
        handleBInput(input);
    }
    else { ... }
  }

  // ...
}

To get a good code coverage, I would like to test, that if I put a list with two Inputs with name A and three with name B , the corresponding internal methods are called twice or three times, respectively.

So I've tried the following:

@Test
public void separatingInputsByName() {
    Input entry1 = mock(Input .class);
    Input entry2 = mock(Input .class);
    Input entry3 = mock(Input .class);

    doReturn("A").when(entry1).getName();
    doReturn("A").when(entry2).getName();
    doReturn("B").when(entry3).getName();

    ClassUnderTest sut = mock(ClassUnderTest .class);

    sut.doSomethingWithInputs(Arrays.asList(entry1, entry2, entry3));

    verify(sut).handleAInput(entry1);
    verify(sut).handleAInput(entry2);
    verify(sut).handleBInput(entry3);
}

Unfortunately this does not lead to a proper invocation of the internal methods, probably because the class under test is mocked, so the method implementation is different.

How can I test/verify a method like this properly?

Answer 1

You should use spy() , not mock() .

When you use mock() , all methods are "overriden" so that default actions are taken instead of calling the real methods; spy() will simply register method invocations.

Therefore:

ClassUnderTest sut = spy(new ClassUnderTest(...));

sut.doSomethingWithInputs(Arrays.asList(entry1, entry2, entry3));

verify(sut).handleAInput(entry1);
verify(sut).handleAInput(entry2);
verify(sut).handleBInput(entry3);
verifyNoMoreInteractions(sut); // if necessary

Also, you can:

when(entry1.getName()).thenReturn("A");

Personally, I find it easier to read, but that's a matter of taste, of course.

Also, you can use InOrder in your case:

final InOrder inOrder = inOrder(sut);

inOrder.verify(sut).handleAInput(entry1);
// etc