crew_test("prevent infinite loop of failed worker launches", {
  x <- crew_controller_local(
    workers = 1L,
    seconds_idle = 1e-9,
    launch_max = 3L
  )
  x$start()
  expect_equal(x$launcher$workers$futile, 0L)
  x$launch(n = 1L)
  # Pause until worker idles out.
  Sys.sleep(5)
  expect_equal(x$launcher$workers$futile, 0L)
  x$launch(n = 1L)
  # Pause until worker idles out.
  Sys.sleep(5)
  expect_equal(x$launcher$workers$futile, 1L)
  private <- crew_private(x$launcher)
  private$.seconds_idle <- Inf
  x$push(TRUE)
  x$wait()
  expect_equal(x$launcher$workers$futile, 2L)
  x$launcher$terminate_workers(index = 1L)
  # Pause until worker exits.
  Sys.sleep(5)
  private$.seconds_idle <- 1e-9
  x$launch(n = 1L)
  # Pause until worker exits.
  Sys.sleep(5)
  expect_equal(x$launcher$workers$futile, 0L)
  x$launch(n = 1L)
  # Pause until worker exits.
  Sys.sleep(5)
  expect_equal(x$launcher$workers$futile, 1L)
  x$launch(n = 1L)
  # Pause until worker exits.
  Sys.sleep(5)
  expect_equal(x$launcher$workers$futile, 2L)
  x$launch(n = 1L)
  # Pause until worker exits.
  Sys.sleep(5)
  expect_equal(x$launcher$workers$futile, 3L)
  expect_error(x$launch(n = 1L), class = "crew_error")
  x$terminate()
})