title: Testing Mono.delay with StepVerifier
body: <p>I'm trying to test <code>Mono.delay</code> using <code>StepVerifier</code>.
  My code is as follow:</p>
  
  <pre><code>Mono[Long] mono = Mono.delay(Duration.ofDays(5));
  
  StepVerifier.withVirtualTime(() -&gt; mono)
      .thenAwait(Duration.ofDays(5))
      .expectNextCount(1)
      .expectComplete()
      .verify();
  </code></pre>
  
  <p>And I'm getting the following stacktrace</p>
  
  <pre><code>expectation "expectNextCount" failed (expected: count = 1; actual: counted = 0; signal: onError(reactor.core.Exceptions$BubblingException:
  java.util.concurrent.RejectedExecutionException: Scheduler unavailable))
  java.lang.AssertionError: expectation "expectNextCount" failed (expected: count = 1; actual: counted = 0; signal: onError(reactor.core.Exceptions$BubblingException: java.util.concurrent.RejectedExecutionException: Scheduler unavailable))
  at reactor.test.DefaultStepVerifierBuilder.failPrefix(DefaultStepVerifierBuilder.java:1679)
  at reactor.test.DefaultStepVerifierBuilder.fail(DefaultStepVerifierBuilder.java:1675)
  at reactor.test.DefaultStepVerifierBuilder$DefaultVerifySubscriber.checkCountMismatch(DefaultStepVerifierBuilder.java:886)
  at reactor.test.DefaultStepVerifierBuilder$DefaultVerifySubscriber.onSignalCount(DefaultStepVerifierBuilder.java:1112)
  at reactor.test.DefaultStepVerifierBuilder$DefaultVerifySubscriber.onExpectation(DefaultStepVerifierBuilder.java:963)
  at reactor.test.DefaultStepVerifierBuilder$DefaultVerifySubscriber.onError(DefaultStepVerifierBuilder.java:727)
  at reactor.core.publisher.MonoDelay.subscribe(MonoDelay.java:59)
  at reactor.test.DefaultStepVerifierBuilder$DefaultStepVerifier.verify(DefaultStepVerifierBuilder.java:532)
  at reactor.test.DefaultStepVerifierBuilder$DefaultStepVerifier.verify(DefaultStepVerifierBuilder.java:508)
  </code></pre>
  
  <p>After tracing the source code, it seems that the executors are shutdown on the method <code>Schedulers.setFactory</code></p>
  
  <p>I'm wondering if I'm missing something here.</p>