Y25-649 - [BUG] JS scripts are not included in test coverage stats for feature tests

[StephenHulme]

Describe the bug
JS scripts are not included in test coverage stats for feature tests.
This results in an incorrect calculation (underestimate) of test coverage.

To Reproduce
Steps to reproduce the behaviour:

1. See [ux] Improve unsuitable error message #2616

Expected behaviour
Test coverage reflects addition of new rspec feature test for javascript code change.

Additional context
Add any other context about the problem here.