assertThat(taskFaker.executeCallCount).isEqualTo(1)
  }

  @Test fun noMoreThanOneWorkerThreadWaitingToStartAtATime() {
    // Enqueueing the red task starts a thread because the head of the queue changed.
    redQueue.execute("red task") {
      log += "red:starting@${taskFaker.nanoTime}"
      taskFaker.sleep(100.µs)
      log += "red:finishing@${taskFaker.nanoTime}"
    }

    List<String> freshlyAdded = newArrayList("freshly", "added");

    boolean changed = Iterables.addAll(alreadyThere, freshlyAdded);
    assertThat(alreadyThere).containsExactly("already", "there", "freshly", "added").inOrder();
    assertTrue(changed);
  }

  private static void assertCanIterateAgain(Iterable<?> iterable) {

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Dependencies with `yield` have evolved over time to cover different use cases and fix some issues.