WebStorm not recognising Mocha describe() and it()<>
This question already has an answer here:
From the description of the inspection:
Navigate to the above referenced preference and make sure the @types/mocha (this was changed in early 2019 from mocha-DefinitelyTyped. Either is OK.) library is in the list (don't select it). If it is not in the list, click the Download... button, find mocha there, and add it. Then click the Manage Scopes... button, find your test directory, click on the library column, and select the @types/mocha entry. See the screenshot below.
This answer might help you: Mocha's describe "require() is missing" in WebStorm 11. It explains how to disable specific inspections for specific folders, which can be useful when working with Mocha. So it is a different approach to installing the mocha-definatelyTyped library.