Question

A developer asks Copilot Chat to generate unit tests for a `calculateDiscount(price, tier)` function. Copilot produces tests that all pass, but a subsequent mutation testing run reveals that several mutants (e.g., changing `>=` to `>`, or `*0.9` to `*0.8`) survive because no test fails when the logic is altered. What is the most effective way to use Copilot to address this gap?

Accepted Answer

Prompt Copilot to add assertions that verify exact computed discount values at boundary tiers, so that any change to the comparison operators or multipliers causes a test to fail.

Answer

Ask Copilot to increase the number of test cases with randomly generated prices, since more inputs will eventually catch the surviving mutants.

Answer

Instruct Copilot to wrap each test in a try/catch block so exceptions from mutated code are reported as failures.

Answer

Have Copilot lower the code coverage threshold so the surviving mutants are excluded from the report.