I'm in the process of creating a unit test and I'm trying to optimize it by creating a helper file to replace some repeated code. In doing so some of my expects will end up in this helper file, as it is written now. I'm using the Mocha testing framework and the Chai assertion library.

My questions are:

  1. Is it ok for these expects to be in the helper file?
  2. Is it best practice to keep all expects located within the test file?

1 Answer 1


The concept of a unit test is that that test can run as a self contained test. It will test one behavior is true/false.

Using helper files is fine as long as changes are consistent and won't affect the behavior of previously written tests. In other words, you shouldn't put anything in your helper that is unique to a single test.

  • That makes sense. I'm just thinking from a peer reviewer point of view and for future maintenance. When looking at the test file it may seem as though some test cases are absent when they are in fact in the helper file. I wasn't sure if there was a general best practice for this. In my opinion it would be best to have all test assertions in the main file to quickly view all that's explicitly being tested.
    – sashak007
    Commented Jan 18, 2016 at 22:32
  • you want the assertions of the test you want to accomplish in the 'main' file, that is correct. But for example i have an isLoader() in my 'helper' file. This asserts the page loaded and it didnt go to a 404. The distinction is "Test X tests X" the loading of the page is not what X is testing
    – ECiurleo
    Commented Jan 19, 2016 at 8:31
  • 1
    That's true, I see what saying. I generally err on oversharing, especially when there's many hands potentially sharing the same code base. But it's much more burdensome to recreate functions so all assertions are in the 'main' file - esp when it's not what's being explicitly tested. Thanks for your reply!
    – sashak007
    Commented Jan 24, 2016 at 5:31

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