在Elixir中测试异步代码 [英] Testing asynchronous code in Elixir

问题描述

我想测试使用 Task.async

的功能，以便通过测试，我需要在声明前使其休眠100毫秒，否则测试过程将在执行异步任务之前终止。

In order to make my test pass, I need to make it sleep for 100ms before assertions, otherwise the test process is killed before the async task is executed.

有没有更好的方法？

编辑，添加代码示例：

我想测试的代码（大致）：

The code I would like to test (roughly) :

def search(params) do
  RateLimiter.rate_limit(fn ->
    parsed_params = ExTwitter.Parser.parse_request_params(params)
    json = ExTwitter.API.Base.request(:get, "1.1/search/tweets.json", parsed_params)
    Task.async(fn -> process_search_output(json) end)
    new_max_id(json)
  end)
end

我已经编写的测试（仅适用于睡眠调用）。

And the test I already wrote (working only with the call to sleep)

test "processes and store tweets" do
  with_mock ExTwitter.API.Base, [request: fn(_,_,_) -> json_fixture end] do
    with_mock TwitterRateLimiter, [rate_limit: fn(fun) -> fun.() end] do
      TSearch.search([q: "my query"])
      :timer.sleep(100)
      # assertions 
      assert called TStore.store("some tweet from my fixtures")
      assert called TStore.store("another one")
    end
  end
end

推荐答案

由于问题有点含糊，我在这里给出一般性的答案。通常的技术是监视过程并等待出现故障消息。像这样：

Since the question is a bit vague, I will give the general answer here. The usual technique is to monitor the process and wait for the down message. Something like this:

task = Task.async(fn -> "foo" end)
ref  = Process.monitor(task.pid)
assert_receive {:DOWN, ^ref, :process, _, :normal}, 500

一些重要的事情：

• 元组的第五个元素是退出原因。我声称任务出口为：normal 。如果您期望另一个出口，请相应地进行更改。

• The fifth element of the tuple is the exit reason. I am asserting the Task exit is :normal. Change that accordingly if you are expecting another exit.

assert_receive 中的第二个值是超时。假设您目前有100毫秒的睡眠时间，那么500毫秒听起来是一个合理的数目。

The second value in assert_receive is the timeout. 500 miliseconds sounds like a reasonable amount given you currently have a 100 ms sleep.

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