Metric-imp converter passing all internal tests, but failing cert test

The project is passing all internal Mocha tests, but fails on the FCC site itself. These are the two tests failing:

  1. You can convert 'mi' to 'km' and vice versa. (1 mi to 1.60934 km)

  2. All incoming units should be accepted in both upper and lower case, but should be returned in both the initUnit and returnUnit in lower case, except for liter, which should be represented as an uppercase 'L' .

Even testing these scenarios manually on the rendered site doesn’t yield these errors. Maybe I’ve just missed something obvious, but I can’t for the life of me figure it out.

Your project link(s)

solution: https://replit.com/@windowpuncher/boilerplate-project-metricimpconverter

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User Agent is: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/96.0.4664.45 Safari/537.36

Challenge: Metric-Imperial Converter

Link to the challenge: