jasmine test mocking a function by calling spyOn

Question

I am pretty new in Jasmine test.

Lett say I have this sample.js file:

(function() {

    function myFunction() {

        do some thing and then make a call to MyOtherFunciton
    }

    myOtherFunciton(p1, p2, p3) {
        //do some stuff in here 
    }
    module.exports = {
      myOtherFunciton,
      myFunction
    }
})();

Now I have this jasmine test does the following

   const mySampleFile = require(./sample.js);

   spyOn(mySampleFile, "myOtherFunciton").and.callFack(()=>{
   });
   mySampleFile.myFunction();
   expect(mySampleFile.myOtherFunciton).toHaveBeenCalled();

The problem I am experiencing is that it makes a call to real myOtherFunciton function but not the mocked one. Why is that ?

Answer 1

It's a function scope problem you are running into. The function myOtherFunciton() called from within myFunction() is not the same as mySampleFile.myOtherFunciton(), as you found out. To fix will require a slight refactor of your original code (don't you love it when testing exposes such things?). I added some console.logs below just to be clear where the execution context is going during testing.

Suggested refactor:

(function() {

    exports.myFunction = function() {
        // do some thing and then make a call to MyOtherFunciton
        console.log('inside myFunction');
        exports.myOtherFunciton('a', 'b', 'c'); // scoped to exports, now can be mocked
        // myOtherFunciton('a', 'b', 'c'); // <-- don't call it like this: scoped within IIFE
    }

    exports.myOtherFunciton = function(p1, p2, p3) {
        console.log('inside original myOtherFunciton');
        //do some stuff in here 
    }
    // module.exports = {
    //   myOtherFunciton,
    //   myFunction
    // }
})();

Here is a working StackBlitz showing the test now passing. Click on 'console' below the Jasmine test window to see the output.

I hope this helps.