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Clojure: Expectations, Customize your Test Running Context

· Java Zone

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I've previously written about expectations' before run hook and the built in support for detecting state changes. These features are nice for reassigning vars you don't care about or detecting accidental state changes; however, there was no option for temporarily changing the context in which your tests are run. As of expectations 1.4.36, that's no longer true.

Version 1.4.36 allows you to alter the context in which your tests run by creating a function that takes the "run the tests" function as an arg, and do you as wish.

Too abstract, no problem, the code:
(defn in-context
"rebind a var to verify that the expecations are run in the defined context"
{:expectations-options :in-context}
[work]
(with-redefs [success.success-examples-src/a-fn-to-be-rebound (constantly :a-rebound-val)]
(work)))
That's it, if you add the previous function to your tests, you can define whatever you like in the in-context function, and your tests will be run in your custom context. The previous snippet is pulled from the expectations tests, which verify that success.success-examples-src/a-fn-to-be-rebound is correctly rebound. In the expectations tests an expectations_options.clj namespace is used to define in-context (expectations_options.clj explained here).

Why would you want to define your own context? In the past I've used in-context for two reasons: rebinding things I don't care about (e.g. calls to logging) to (constantly true), and rebinding things I never want called (e.g. create a new thread) to #(throw (RuntimeException. "not allowed in tests"))

I've been using in-context for about a month now, and it's worked well for me. Give it a shot and let me know how it's working for you.

 

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Published at DZone with permission of Jay Fields, DZone MVB. See the original article here.

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