### Question:
Part5ResilienceResponsive { @Complexity(EASY) public static Publisher<String> fallbackHelloOnError(Flux<String> failurePublisher) { throw new RuntimeException("Not implemented"); }  @Complexity(EASY) static Publisher<String> fallbackHelloOnEmpty(Flux<String> emptyPublisher); @Complexity(EASY) static Publisher<String> fallbackHelloOnError(Flux<String> failurePublisher); @Complexity(EASY) static Publisher<String> retryOnError(Mono<String> failurePublisher); @Complexity(MEDIUM) static Publisher<String> timeoutLongOperation(CompletableFuture<String> longRunningCall); @Complexity(HARD) static Publisher<String> timeoutLongOperation(Callable<String> longRunningCall);  }### Answer:
@Test public void fallbackHelloOnErrorTest() { StepVerifier .create(fallbackHelloOnError(Flux.error(new RuntimeException()))) .expectSubscription() .expectNext("Hello") .verifyComplete(); }