Coverage gap

An area of a system or requirement that is not addressed by any existing test case, leaving risk undetected. Coverage gaps can arise from vague or incomplete requirements, from tests that focus only on happy paths, or from over-reliance on AI-generated test suites that reflect only what was written in the requirement rather than what was intended. Identifying coverage gaps is one of the areas where AI tools can add genuine value, by surfacing edge cases and scenarios a human tester might overlook. 

For example, a password reset flow tested only for valid inputs would have a coverage gap around expired tokens or malformed email addresses.