strictEqual tests check for both value and type. That being said, the error message is confusing. IMO there are 3 ways to fix this:

1. Remove the custom error message and leave Mocha+Chai handle it. It'll only say the values being different.
2. Add some tests that check the type of the returned value and separate the error messages.
3. Create a function that returns either if the error comes from the value or the type being different.