* thread, which yields its execution privilege while calling [runTasks], [runNextTask], or
 * [advanceUntil]. These functions don't return until the task threads are all idle.
 *
 * Task threads release their execution privilege in these ways:
 *
 *  * By yielding in [TaskRunner.Backend.coordinatorWait].
 *  * By yielding in [BlockingQueue.poll].
 *  * By completing.
 */

    return FakePlan(nextPlanId++).also {
      plans += it
    }
  }

  override fun isCanceled() = canceled

  override fun plan(): FakePlan {
    // Return deferred plans preferentially. These don't require addPlan().
    if (deferredPlans.isNotEmpty()) return deferredPlans.removeFirst() as FakePlan

    if (nextPlanIndex >= plans.size && autoGeneratePlans) addPlan()

    require(nextPlanIndex < plans.size) {

    }
  }

  /**
   * Returns an immediately-executable task for the calling thread to execute, sleeping as necessary
   * until one is ready. If there are no ready queues, or if other threads have everything under
   * control this will return null. If there is more than a single task ready to execute immediately
   * this will start another thread to handle that work.
   */
  fun awaitTaskToRun(): Task? {

      factory.newConnectionPool(
        maxIdleConnections = 2,
      )
    val c1 = factory.newConnection(pool, routeA1, 50L)
    val c2 = factory.newConnection(pool, routeB1, 75L)

    // With 2 connections, there's no need to evict until the connections time out.
    assertThat(pool.closeConnections(100L)).isEqualTo(50L)
    assertThat(pool.connectionCount()).isEqualTo(2)
    assertThat(c1.socket().isClosed).isFalse()

    taskFaker.assertNoMoreTasks()
  }

  /**
   * This test puts several connections in flight that all fail at approximately the same time. It
   * confirms the fast fallback implements these invariants:
   *
   *  * if there's no TCP connect in flight, start one.
   *  * don't start a new TCP connect within 250 ms of the previous TCP connect.
   */
  @Test
  fun minimumDelayEnforcedBetweenConnects() {