如何使用 jest 确保我只使用两个 arguments？

Question

I'm challenging myself to create my own tests for problems in freeCodeCamp. Currently stuck on the second requirement for 'Subtract One Number from Another with JavaScript'. Here are the requirements.

var difference = 45 - 0;

//The variable difference should be equal to 12.
   
 //You should only subtract one number from 45.

How could I write my own test to make sure I am only using two arguments?

(freeCodeCamp problem can be found here: https://www.freecodecamp.org/learn/javascript-algorithms-and-data-structures/basic-javascript/subtract-one-number-from-another-with-javascript )

Answer 1

If you were testing this as part of an application, you wouldn't necessarily be testing the expression itself but rather some function that contains this expression. To organize that code example in a testable way, you could write a function like this:

 function getDifference(numberToSubtract) { const difference = 45 - numberToSubtract; return difference; }

Then you could use Jest to assert the return value is 12 and that you've only used a single argument like this:

expect(getDifference(33)).toBe(12);