* 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? {
    lock.assertHeld()

    while (true) {
      if (readyQueues.isEmpty()) {
        return null // Nothing to do.

  @Suppress("NOTHING_TO_INLINE")
  internal inline fun Any.assertThreadHoldsLock() {
    if (assertionsEnabled && !taskRunner.lock.isHeldByCurrentThread) {
      throw AssertionError("Thread ${Thread.currentThread().name} MUST hold lock on $this")
    }
  }

  @Suppress("NOTHING_TO_INLINE")
  internal inline fun Any.assertThreadDoesntHoldLock() {
    if (assertionsEnabled && taskRunner.lock.isHeldByCurrentThread) {

    // Connections are replaced if they idle out or are evicted from the pool
    evictAllConnections(pool)
    assertThat(pool.connectionCount()).isEqualTo(2)
    forceConnectionsToExpire(pool, expireTime)
    assertThat(pool.connectionCount()).isEqualTo(2)

    // Excess connections aren't removed until they idle out, even if no longer needed
    setPolicy(pool, address, ConnectionPool.AddressPolicy(1))

      object : Task("task") {
        val schedules = mutableListOf(50.µs)
        val delays = mutableListOf(200.µs, -1)

        override fun runOnce(): Long {
          log += "run@${taskFaker.nanoTime}"
          if (schedules.isNotEmpty()) {
            redQueue.schedule(this, schedules.removeAt(0))
          }
          return delays.removeAt(0)
        }
      }
    redQueue.schedule(task, 100.µs)

  }

  /**
   * 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() {