@Override
    public ImmutableSet<E> removed(E e) {
        return new PCollectionsImmutableSet<>(underlying().minus(e));
    }
@Test
    public void testDelegationOfRemoved() {
        new PCollectionsHashSetWrapperDelegationChecker<>()
            .defineMockConfigurationForFunctionInvocation(mock -> mock.minus(eq(this)), SINGLETON_SET)
            .defineWrapperFunctionInvocationAndMockReturnValueTransformation(wrapper -> wrapper.removed(this), identity())
            .expectWrapperToWrapMockFunctionReturnValue()
            .doFunctionDelegationCheck();
    }