Using Artifice to Stub Server Responses

Jamie Hill January 04, 2011

In a recent project I needed a way to fake a response from a server in my Cucumber features. Specifically, I was testing integration with a payment gateway and wanted to stub it’s responses based on different requests.
In the past I have used FakeWeb, however it becomes a little hairy when you need to stub a response based on request body. I came across a couple of alternatives, firstly WebMock which looks promising but then Artifice from the mighty Yehuda Katz caught my eye…
Artifice lets you “replace the Net::HTTP subsystem of Ruby with an equivalent that routes all requests to a Rack application”. I like the simplicity of this solution as you can in essence use a Rack application to replace the responses of the service you are testing.

An Example

First we create a simple Rack application to stand in for the server we are interacting with.

app = proc do |env|
  [200, { "Content-Type"  =&gt; "text/html" },
    ["Hello world: #{env.inspect}"]
  ]
end

Then we simply use Artifice’s “activate_with” method to wrap any requests.

Artifice.activate_with(app) do
  response = Net::HTTP.start("google.com") do |http|
    http.post("/the_url", "foo=bar")
  end
  puts response.body
end

This allows for a Rack app to be used as a stand in for a complete API, it could be a Sinatra app for example allowing for easy route handling. We could go so far as to have a series of Rack apps that can be used as stand-ins for common API’s.