@Override
    public boolean addAll(Collection<? extends E> c) {
        // will throw UnsupportedOperationException; delegate anyway for testability
        return underlying().addAll(c);
    }
@Test
    public void testDelegationOfUnsupportedFunctionAddAll() {
        new PCollectionsHashSetWrapperDelegationChecker<>()
            .defineMockConfigurationForUnsupportedFunction(mock -> mock.addAll(eq(Collections.emptyList())))
            .defineWrapperUnsupportedFunctionInvocation(wrapper -> wrapper.addAll(Collections.emptyList()))
            .doUnsupportedFunctionDelegationCheck();
    }