Stub out internal function calls in Midje

0
votes

I'm testing a function that uses two other functions from other namespace.

(fact "a test"
      (let [result (function-that-uses-functions-from-other-namespace)]
      result => truthy))

I want to stub out the functions from other namespace and I'm having problems writing the test. 

(fact "a test"
      (let [result (function-that-uses-functions-from-other-namespace)]
          (function-that-uses-functions-from-other-namespace)
          (provided (other-namespace/function1 "parameter") => "stub_response"))

but this approach don't seem to work. Any hints? Is it simply the case of let being evaluated before checkables as suggested in Using midje provided in a let clause doesn't stub methods

3
clojuremidje
Could you update your example? You don't seem to use result anywhere in the second example and you seem to invoke the the same function twice. So it's not clear to me what your second code snippet is trying to achieve. In general, this structure cannot work and yes you're exactly right, the problem is covered by the question you link to. - joelittlejohn

3 Answers

4
votes

You could use against-background that will stub out function calls not only for single facts but whole fact forms:

(fact "a test"
      ...
      (against-background
        (other-namespace/function1 "parameter") => "stub_response"))

Actually, that would probably have worked for the question you linked, too.

0
votes

Try without the let as it would execute the function immediately, before the prerequisites are set up:

(fact "a test"
  (function-that-uses-functions-from-other-namespace) => truthy
  (provided (some-internal-func arg1 arg2) => some-result
            (other-internal-func) => other-result))

You just need to have the functions to be stubbed required. They can be from another namespace.

Note that protocol methods cannot be stubbed this way.

0
votes

Does it work using (prerequisite)? Something like this:

(fact "a test"
  (prerequisite (other-namespace-function1 "parameter) => "stub_response")
  (function-that-uses-functions-from-other-namespace) => truthy))

That should let you specify return values for any old function you like, which will be replayed when you run the actual fact.

Have a look at fact-wide-prerequisites. I much prefer this to provided, because it lets me stick to a given-when-then style of testing, still using the same syntax as the actual checkers.