Review Summary

Your tests for isIsogram meet all of the stated requirements, so your solution is approved. You correctly cover all the example cases (playgrounds, look, Adam, '', Oops) and assert the expected boolean results using Jest. The tests also properly verify case-insensitivity (e.g., Adam, Oops) and the rule that an empty string should be considered an isogram. Each it block has a clear, unique description, which makes the test suite easy to read and understand. There are no critical issues or missing requirements based on the task description. Nicely done keeping the tests focused, accurate, and aligned with the problem’s constraints.

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