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Testing API Integrations In RSpec

Mark Mzyk | March 5, 2012

RSpec, a Behavior Driven Development framework, is great for various kinds of testing, such as unit and integration testing. However one area that is hard to test is integrations that cross APIs. You call into a service, then need to wait while it takes some action before proceeding with the test you want. An example of this would be inserting an item into a search service, then querying the service to test the output, ensuring your item is there. The service might have a queue and so doesn’t insert the item immediately. How do you test this?

One way is to call the API, sleep, and then run the test. The problem with this is that you have to wait the entire sleep duration for every test run, even if the results are ready before the sleep is done. RSpec’s and Ruby’s flexibility allow you to avoid this situation by writing a helper function:

def wait(time, increment = 5, elapsed_time = 0, &block)
  begin
    yield
  rescue Exception => e
    if elapsed_time >= time
      raise e
    else
      sleep increment
      wait(time, increment, elapsed_time + increment, &block)
    end
  end
end

To use this function, you pass your test to it as a block. The wait function will immediately try the test. If a failure is reported – which in RSpec is just an exception – the function catches the failure and sleeps. The assumption is that a failure means the API that is called into has not yet completed the action that is being waited upon. The wait function continues to retry the test until the test either passes or until it reaches the timeout that was passed to it, at which point it will raise the last error it caught, which will be the last failure of the test it ran.

The wait function has the benefit of returning successes as soon as they are encountered, so the tests don’t have to sleep for the entire duration specified. However, it still has to wait the entire sleep period for a failure, because it can’t distinguish a legitimate failure from the API service not yet returning the correct results.

Using the wait function in an RSpec test looks like this:

describe "a test" do
  before :each do
    insert_user_remote_service("user")
  end

  after :each do
    delete_user_remote_service("user")
  end

  it "should receive the results it expects from the api" do
    wait 30 do
      search_for_user_in_remote_service("user").should == "user"
    end
  end
end

Filed in: Programming.

2 Comments

  1. Pingback from Testing API Integrations In RSpec | Free as in Time:

    […] Testing API Integrations In RSpec, by Mark Mzyk. This entry was posted in Technology and tagged coding, rspec, Ruby, testing. Bookmark the permalink. ← DevOps and Drupal Presentation […]

    March 13, 2012 @ 18:49
  2. Comment by Greg:

    Thanks very helpful. Was getting flakey results with
    wait_until do
    page.evaluate_script(‘$.active’) == 0
    end

    but this did the trick.

    March 28, 2013 @ 10:20