@Test
public void diffDelegatesToFieldAddition() {

    final Scalar<Object> first = new Scalar.Default<>(new Object());
    final Scalar<Object> second = new Scalar.Default<>(new Object());
    final MkAddition<Object> add = new MkAddition<>(new Object());
    final SpyField<Object> field = new SpyField<>(
        new MkField<Object>(new Object(), add)
    );
    new Diff<>(first, second).value(field);
    MatcherAssert.assertThat(
        field.calls().additioned(), Matchers.is(true)
    );
    MatcherAssert.assertThat(
        add.inverted(), Matchers.is(true)
    );
    MatcherAssert.assertThat(
        add.added(), Matchers.greaterThan(0)
    );
}