### test/test_helper.exs
ExUnit.start()

# create some status that your external server could respond with
# you just need to do it once for you entire test suite.
FakeServer.Status.create(:status200, %{response_code: 200, response_body: ~s<"username": "mr_user">})
FakeServer.Status.create(:status500, %{response_code: 500, response_body: ~s<"error": "internal server error">})
FakeServer.Status.create(:status403, %{response_code: 403, response_body: ~s<"error": "forbidden">})

# you can also pass `response_header` (optional):
FakeServer.Status.create(:status200, %{response_code: 200, response_body: "OK", resonse_headers: %{"Conent-Length": 5}})


### test/user_test.exs
defmodule UserTest do
  use ExUnit.Case

  setup_all do
    # you can run a single server on a test file
    # start a fake server with an empty status_list
    # you can ignore the third param if you want the server to run on a random port
    # when using a global server, make sure :async option is set to false on ExUnit
    {:ok, address} = FakeServer.run(:external_server, [], %{port: 5000})

    # point your application to the new fake server
    System.put_env(:external_server_url, address)

    # you can use ExUnit callback to stop the server
    on_exit fn ->
      FakeServer.stop(:external_server)
    end
  end

  test "#get returns user if the external server responds 200" do
    # add the status sequence will want the server to respond with
    # the fake server will respond with the first status on the list
    # after that, that status will be removed
    # this repeats for every request you make
    # if the list empties, the server will respond 200.
    FakeServer.modify_behavior(:external_server, :status200)

    # make the request to the fake server and validate it works
    assert User.get == %{username: "mr_user"}
  end

  test "#get retry up to 3 times when external server responds with 500" do
    {:ok, address} = FakeServer.modify_behavior(:external_server, [:status500, :status500, :status500, :status200])

    # you can easily test a retry scenario, where one call to the external service makes multiple requests
    assert User.get == %{username: "mr_user"}
  end

  test "#get returns timeout after 3 retries" do
    # another retry example, this time with a timeout scenario
    {:ok, address} = FakeServer.modify_behavior(:external_server, [:status500, :status500, :status500, :status500])
    assert User.get == %{error: "timeout", code: 408}
  end

  test "#get serves stale when external server is down" do
    {:ok, address} = FakeServer.modify_behavior(:external_server, [:status200, :status500])

    # our application saves cache on the first successfull response
    # so we make a get request with a 200 response from fake server to save some cache
    User.get

    # the second response from fake server is 500, but there is cache!
    # that's how we know the stale is working
    assert User.get == %{username: "mr_user"}
  end
end

def deps do
  [{:fake_server, "~> 0.4.1", only: :test}]
end