Can't seem to get helper unit test to pass


I’m not sure what’s happening here but I can’t get the unit test generated for my handlebars helper to pass, even though it works when I actually test in development.

Here is the test

test('Returns a string pointing to the cropped version of an image', function(assert) {
  var result = croppedImage("5579-pkUaYMcLSn.png");

And the code to make it pass (should be)

let image = params[0],
    index = image.indexOf('.');
var croppedImageValue = [image.slice(0, index), '-cropped', image.slice(index)].join('');
return croppedImageValue;

Like I said, this code works when testing in development but the unit test won’t pass.

I found this stack overflow here

But I tried switching to the format he shows with the _rawFunction but that just tells me _rawFunction is not a function or something like that.