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FakeServer integrates with ExUnit to make external APIs testing simpler
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FakeServer is an HTTP server that simulates responses. It can be used in test and development environments, helping to validate the behavior of your application if there are errors or unexpected responses from some external HTTP service.

It provides the test_with_server macro to be used together with ExUnit, making it easier to write tests that need to request external services. Instead of creating a mock when you need make a request, you can use a real HTTP server that will reply a deterministic response. This way you can validate if your application can handle it.

FakeServer can also be used through functions, when ExUnit is not available (in the console, for example).


Important: From the version 2.0, FakeServer only supports cowboy 2.x. If you have cowboy 1.x as dependency, use FakeServer version 1.5.

FakeServer is available on Hex. First, add it to mix.exs as a test dependency:

def deps do
    {:fake_server, "~> 2.0", only: :test}

Then, start fake_server application on test/test_helper.exs.

{:ok, _} = Application.ensure_all_started(:fake_server)

Basic Usage

For more examples you can see the docs.


FakeServer provides the macro FakeServer.test_with_server. It works like ExUnit's test macro, but before your test starts it will run an HTTP server in a random port (by default). The server will be available until test case is finished.

You can use the FakeServer.route macro to add a route and setup it's response. Use FakeServer.http_address to get the address of the server running in the current test. Each test will start its own HTTP server.

defmodule MyTest do
  use ExUnit.Case
  import FakeServer

  test_with_server "returns 404 if a request is made to a non-configured route" do
    response = HTTPoison.get!("#{FakeServer.address}/not/configured")
    assert response.status_code == 404

  test_with_server "when the response is a structure it returns the given response" do
    route "/test", Response.no_content!()
    response = HTTPoison.get!("#{FakeServer.address}/test")
    assert response.status_code == 204

  test_with_server "when the response is a list it returns the first element of the list and removes it" do
    route "/test", [Response.ok!(), Response.no_content!()]
    response = HTTPoison.get!("#{FakeServer.address}/test")
    assert response.status_code == 200
    response = HTTPoison.get!("#{FakeServer.address}/test")
    assert response.status_code == 204

  test_with_server "when the response is a function it runs the function" do
    route "/say/hi", fn(_) -> IO.puts "HI!" end
    response = HTTPoison.get! "#{FakeServer.address}/say/hi"

  test_with_server "computes hits for the corresponding route" do
    route "/test", Response.no_content!()
    assert hits() == 0
    assert hits("/test") == 0
    assert hits() == 1
    assert hits("/test") == 1

  test_with_server "supports inline port configuration", [port: 55_000] do
    assert FakeServer.port() == 55_000

Standalone Server

You can use a fake server without ExUnit with FakeServer.start and other helper functions available. Functions work similar to macros, but can be used outside the tests.

iex> {:ok, pid} = FakeServer.start(:my_server)
{:ok, #PID<0.302.0>}

iex> :ok = FakeServer.put_route(pid, "/say/hi", fn(_) -> IO.puts "HI!" end)

iex> {:ok, port} = FakeServer.port(:my_server)
{:ok, 62698}

For more examples you can see the docs.

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