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Ensuring Elixir Application Performance with Testing and ExUnit

Building an Ad-hoc HTTP Server

Explore how to create an ad-hoc HTTP server in Elixir using Plug and Cowboy to mimic a weather API. Learn to configure endpoints, integrate with test environments, and write tests that accurately simulate external dependencies for reliable integration and end-to-end testing.

We'll cover the following...

Let’s go back to the weather API use case.

Elixir
#file path -> soggy_waffle/lib/soggy_waffle/weather_api.ex
  @behavior SoggyWaffle.WeatherAPI.Behavior
  @spec get_forecast(String.t()) ::
          {:ok, map()} | {:error, reason :: term()}
  def get_forecast(city) when is_binary(city) do
    app_id = SoggyWaffle.api_key()
    query_params = URI.encode_query(%{"q" => city, "APPID" => app_id})
    url =
      "https://api.openweathermap.org/data/2.5/forecast?" <> query_params
    case HTTPoison.get(url) do
      {:ok, %HTTPoison.Response{status_code: 200} = response} ->
        {:ok, Jason.decode!(response.body)}
      {:ok, %HTTPoison.Response{status_code: status_code}} ->
        {:error, {:status, status_code}}
      {:error, reason} ->
        {:error, reason}
    end
  end

The weather API exposes a GET /data/2.5/forecast endpoint that we hit from our application. This endpoint accepts two parameters in the query string:

  • Parameter q represents the query.
  • APPID, which identifies the credentials of our application.

The endpoint returns a 200 OK HTTP response with a JSON body containing information about the ...