Referencing Issue #17387 in freeCodeCamp/freeCodeCamp:
In the "Debugging: Understanding the Differences between the freeCodeCamp and Browser Console" challenge, a correct solution cannot pass because of a test failing due to the following:

// running test
invalid regexp group
// tests completed

It has been determined that this is likely because the negative look behind regular expression used is not fully implemented in Firefox yet.

To Reproduce
Steps to reproduce the behavior:

1. Go to the challenge.
2. Solve the challenge per instructions.
3. Run the Tests.

Expected behavior
The challenge should pass if the regular expression in the test is changed (this will be duplicating a PR that was closed under freeCodeCamp/freeCodeCamp so that it can be implemented here).

Desktop (please complete the following information):

• OS: macOS High Sierra v10.13.5
• Browser: Firefox
• Version: 60.0.2