javagenericstestingjunitmockito

Having an issue with mocking a method which has a generic (? extends Collection) return type

I am having a problem with mocking a method with mockito that looks like the following:

Map<Foo, ? extends Collection<Bar>> getValue();

The following is how I am using it in the test:

model = Mockito.mock(Model.class);
Map<Foo, List<Bar>> value = new HashMap<Foo, List<Bar>>();
Mockito.when(model.getValue()).thenReturn(value);

It gives the following error:

error: no suitable method found for thenReturn(Map<Foo,List<Bar>>)

Solution

  • You may use the following:

    model = Mockito.mock(Model.class);
final Map<Foo, List<Bar>> value = new HashMap<Foo, List<Bar>>();

Mockito.when(model.getValue()).thenAnswer(new Answer<Map<Foo, List<Bar>>> () {
  public Map<Foo, List<Bar>> answer(InvocationOnMock invocation) throws Throwable {
    return value;
  }
});

    Above can be shortened using lambda as:

    Mockito.when(model.getValue()).thenAnswer(invocationOnMock -> value)