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Harper: Dead-simple, out-of-process, HTTP mocks

To mock a service using as Harper, POST a mock definition to Harper before making your request. It's simple, and you've probably written something similar a half-dozen times. Well, you don't need to anymore.

You might be interested in using Harper when you're building an app that depends on an HTTP service, but you can't mock it out in-process. For example, a single page JavaScript app running in a mobile browser.

Ruby Client API

Unfortunately there aren't yet interfaces to Harper from other languages.

  • Use HarperClient::start to start the Harper service in the background.

  • Use HarperClient::stop to stop the background service.

These two calls do start and stop another Ruby interpreter running in the background, so you might want to run these at the beginning and the end of your cucumber run, rather than before and after every scenario.

This interface is incomplete. It is also possible to delete a mock. This can be done by deleting the URL provided in the Location header when creating a new mock.

If you require more control of Harper, or you want to support a new language, check out features/mock_http_rpc_service.feature. And pull requests are always welcomed.

Defining Mocks

Use HarperClient::mock to define a new mock. This method takes a hash defining the mock. If a mock has already been defined for a URL, Harper will silently replace it with the new mock.

  • url: The URL path to mock out. This also identifies the mock. Required.

  • method: The HTTP method to respond to. Required.

  • status: The HTTP status code to provide. Optional. Defaults to 200.

  • content_type: What content-type header to set when responding with the mock. Required.

  • body: Either a string to be used as the HTTP response body, or an array of strings. If an array is provided Harper will cycle through the array as the response body for requests. Required.

  • delay: A delay to include when responding to the mock, in milliseconds. Optional. Defaults to no delay.

  • cookies: This is a hash of key value pairs of cookies that harper will send back in the mock response. For example:

    harper.mock :method => "POST", :url => "/url", :'content-type' => "application/xml", :body => "response body", :cookies => {"UserID" => "JohnDoe", "sampleCookie" => "cookieValue"}

  • request_body: The params are used to compare with the actual request body to find out whether the mock applies. This request_body is optional and is required only in scenarios where you want multiple requests to the same url return different response based on some parameter sent in the request. The value passed in can actually be xml read from a file, json read from a file or simply values in the request. They need not be the whole request body - partial request params work. However these must be conspicuously different across the requests i.e they should not be so generic that they appear in all requests to that url.

  • request_cookies: This is a hash of key value pairs of cookies being expected in the actual request, which will be used by harper for matching before sending back the mock response. For example:

    harper.mock :method => "POST", :url => "/url", :'content-type' => "application/xml", :request_body => request_json, :body => "response body", :request_cookies => {"UserID" => "JohnDoe"}

Typical Use

  1. Start Harper at the very start of your test run.
  2. In the Given steps or Background for your scenarios, define the mocks that will be required for that scenario. If a similar mock has already been defined, Harper will silently replace it.
  3. At the very end of your test run, stop Harper.

That's it.