Testing Asynchronous OTP

Transcript

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22. defmodule RollingAverage do
    
    
    use GenServer
    
    
    def start_link(limit), do: # ...
    
    
    def add(pid, n), do: # ...
    
    
    

    def average(pid), do: # ...
    
    
    end
    

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25. test "add/2" do
    
    
    {:ok, pid} = RollingAverage.start_link()
    
    
    RollingAverage.add(pid, 3)
    
    
    # Now what?
    
    
    end
    

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27. test "add/2 and average/1" do
    
    
    {:ok, pid} = RollingAverage.start_link(2)
    
    
    RollingAverage.add(pid, 3)
    
    
    RollingAverage.add(pid, 4)
    
    
    assert RollingAverage.average(pid) == 3.5
    
    
    RollingAverage.add(pid, 5)
    
    
    assert RollingAverage.average(pid) == 4.5
    
    
    end
    

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29. defmodule RollingList do
    
    
    def new(limit), do: {limit, []}
    
    
    def add({limit, list}, n), do: # ...
    
    
    
    
    def average({_limit, list}), do: # ...
    
    
    end
    

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30. test "add/2" do
    
    
    rolling_list = RollingList.new(2)
    
    
    assert RollingList.add(rolling_list, 3) ==
    
    
    {_limit = 2, [3]}
    
    
    end
    

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32. test "add/2" do
    
    
    {:ok, pid} = RollingAverage.start_link(2)
    
    
    RollingAverage.add(pid, 3)
    
    
    state = :sys.get_state(pid)
    
    
    assert state == {_limit = 2, [3]}
    
    
    end
    

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35. test "add/2 and average/1" do
    
    
    {:ok, pid} =
    
    
    start_supervised(
    
    
    {RollingAverage, _limit = 2}
    
    
    )
    
    
    # Same as before
    
    
    end
    

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37. def background_work do
    
    
    Task.start(fn ->
    
    
    do_something()
    
    
    end)
    
    
    end
    

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40. def background_work(parent, ref) do
    
    
    Task.start(fn ->
    
    
    do_something()
    
    
    send(parent, {ref, :done})
    
    
    end)
    
    
    end
    

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41. test "background_work/0" do
    
    
    ref = make_ref()
    
    
    background_work(self(), ref)
    
    
    assert_receive {^ref, :done}
    
    
    end
    

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43. def background_work do
    
    
    Task.start(fn ->
    
    
    :ok = twitter_module.post()
    
    
    end)
    
    
    end
    

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44. test "background_work/0" do
    
    
    parent = self()
    
    
    ref = make_ref()
    
    
    Mox.expect(TwitterMock, :post, fn ->
    
    
    send(parent, ref)
    
    
    :ok
    
    
    end)
    
    
    background_work()
    
    
    assert_receive ^ref
    
    
    end
    

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46. defmodule WeatherChecker do
    
    
    use GenServer
    
    
    def init(_) do
    
    
    :timer.send_interval(5000, self(), :tick)
    
    
    end
    
    
    def handle_info(:tick, _) do
    
    
    check_weather()
    
    
    end
    
    
    end
    

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47. test "checking weather periodically" do
    
    
    {:ok, _pid} = WeatherChecker.start_link()
    
    
    Process.sleep(5000 * 1.5)
    
    
    assert weather_checked?()
    
    
    end
    

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49. defmodule WeatherChecker do
    
    
    use GenServer
    
    
    def init(_) do
    
    
    :timer.send_interval(5000, self(), :tick)
    
    
    end
    
    
    def tick(pid), do: send(pid, :tick)
    
    
    def handle_info(:tick, _) do
    
    
    check_weather()
    
    
    end
    
    
    end
    

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50. test "checking weather periodically" do
    
    
    {:ok, pid} = WeatherChecker.start_link()
    
    
    WeatherChecker.tick(pid)
    
    
    assert weather_checked?()
    
    
    end
    

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51. defmodule WeatherChecker do
    
    
    use GenServer
    
    
    def init(:interval) do
    
    
    :timer.send_interval(5000, self(), :tick)
    
    
    end
    
    
    def init(:manual) do
    
    
    # No send_interval
    
    
    end
    
    
    end
    

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53. @mix_env Mix.env()
    
    
    def start(_type, _args) do
    
    
    Supervisor.start_link(children(@mix_env), ...)
    
    
    end
    
    
    defp children(:test), do: [...]
    
    
    defp children(_env), do: [WeatherChecker | ...]
    

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58. test "cleanup after crashes" do
    
    
    Process.flag(:trap_exit, true)
    
    
    {:ok, pid} = start_supervised(MyServer)
    
    
    Process.exit(pid, :kill)
    
    
    assert cleanup_successful?()
    
    
    end
    

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