qa – In unit testing should I check if a method is being called or just check the result?

It depends on what you are testing.

For pure simple helper as you have here, I may not really bother about them in my test on higher end functions, and have unit test dedicated to the helper function.
But if my helper rely on some external system, I would do some mock to check that the function I want to be called is properly called: If my helper is doing some database query for example, I’d check that the query function/method is properly called, and mock its result if I want to test for specific error.