@Synchronized
  fun queuedCalls(): List<Call> = readyAsyncCalls.map { it.call }.unmodifiable()

  /** Returns a snapshot of the calls currently being executed. */
  @Synchronized
  fun runningCalls(): List<Call> = (runningSyncCalls + runningAsyncCalls.map { it.call }).unmodifiable()

  @Synchronized
  fun queuedCallsCount(): Int = readyAsyncCalls.size

  @Synchronized

    assertThat(dispatcher.queuedCallsCount()).isEqualTo(0)
    assertThat(dispatcher.runningCalls())
      .containsExactlyInAnyOrder(a1, a2)
    assertThat(dispatcher.queuedCalls()).isEmpty()

    // Cancel some calls. That doesn't impact running or queued.
    a2.cancel()
    a3.cancel()
    assertThat(dispatcher.runningCalls())
      .containsExactlyInAnyOrder(a1, a2)
    assertThat(dispatcher.queuedCalls()).isEmpty()