void shutdown() {
      shutdown.set(true);
      while (this.isAlive()) {
        Thread.yield();
      }
    }
  }

  void assertWrapsInterruptedException(RuntimeException e) {
    assertThat(e).hasMessageThat().contains("Unexpected interrupt");
    assertThat(e).hasCauseThat().isInstanceOf(InterruptedException.class);
  }