Mock5

Mock5 allows to mock external APIs with simple Sinatra Rack apps.

Installation

This gem could be useful for testing, and maybe development purposes. Add it to the relevant groups in your Gemfile.

gem "mock5", groups: [:test, :development]

and run bundle.

Usage

mock

Use this method to describe API you're trying to mock.

weather_api = Mock5.mock("http://weather-api.com") do
  get "/weather.json" do
    MultiJson.dump(
      location: "Philadelphia, PA",
      temperature: "60F",
      description: "Sunny"
    )
  end
end

mount

Use this method to enable API mocks you've defined previously.

Mock5.mount weather_api, some_other_api
Net::HTTP.get("weather-api.com", "/weather.json") # => "{\"location\":...

unmount

Unmounts passed APIs if thery were previously mounted

Mock5.unmount some_other_api # [, and_another_api... ]

mounted_apis

This method returns a Set of all currently mounted APIs

Mock5.mounted_apis # => { weather_api }
Mock5.mount another_api
Mock5.mounted_apis # => { weather_api, another_api }

with_mounted

Executes the block with all given APIs mounted, and then unmounts them.

Mock5.mounted_apis # => { other_api }
Mock5.with_mounted weather_api, other_api do
  Mock5.mounted_apis # => { other_api, weather_api }
  run_weather_api_test_suite!
end
Mock5.mounted_apis # => { other_api }

Example

Say you're writing a nice wrapper around remote user management REST API. You want your library to handle any unexpected situation aproppriately and show a relevant error message, or schedule a retry some time later.

Obviously, you can't rely on a production API to test all these codepaths. You probably want a way to emulate all these situations locally. Enter Mock5:

# user registers successfully
SuccessfulRegistration = Mock5.mock("http://example.com") do
  post "/users" do
    MultiJson.dump(
      first_name: "Zapp",
      last_name: "Brannigan",
      email: "zapp@planetexpress.com"
    )
  end
end

# registration returns validation error
UnsuccessfulRegistration = Mock5.mock("http://example.com") do
  post "/users" do
    halt 406, MultiJson.dump(
      first_name: ["is too lame"],
      email: ["is not unique"]
    )
  end
end

# remote api is down for some reason
RegistrationUnavailable = Mock5.mock("http://example.com") do
  post "/users" do
    halt 503, "Service Unavailable"
  end
end

# remote api times takes long time to respond
RegistrationTimeout = Mock5.mock("http://example.com") do
  post "/users" do
    sleep 15
  end
end

describe MyApiWrapper do
  describe "successfull" do
    around do |example|
      Mock5.with_mounted(SuccessfulRegistration, &example)
    end

    it "allows user registration" do
      expect{ MyApiWrapper.register_user }.not_to raise_error
    end
  end

  describe "validation errors" do
    around do |example|
      Mock5.with_mounted(UnsuccessfulRegistration, &example)
    end

    it "raises a valiation error" do
      expect{ MyApiWrapper.register_user }.to raise_error(MyApiWrapper::ValidationError)
    end
  end

  describe "service is unavailable" do
    around do |example|
      Mock5.with_mounted(RegistrationUnavailable, &example)
    end

    it "raises a ServiceUnavailable error" do
      expect{ MyApiWrapper.register_user }.to raise_error(MyApiWrapper::ServiceUnavailable)
    end
  end

  describe "timeout" do
    around do |example|
      Mock5.with_mounted(RegistrationTimeout, &example)
    end

    it "raises timeout error" do
      expect{ MyApiWrapper.register_user }.to raise_error(Timeout::Error)
    end
  end
end

Contributing

1. Fork it
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Add some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create new Pull Request