public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
            invokedMethodSignatures.add(method.toString());
            if (method.getName().startsWith("is")) {
                return true;
            }
            return null;
        }
Test that all SubstituteLogger methods invoke the delegate, except for explicitly excluded  methods.
slf4j-api/src/test/java/org/slf4j/helpers/SubstitutableLoggerTest.java