How to compare coding assistants when both can pass the same test

When two coding assistants both pass the same test, compare the path they took, not only the green result.

A passing test is necessary, but it does not reveal whether the assistant understood the codebase, preserved user changes, avoided unrelated refactors, added the right guardrail, or left the system easier to maintain. Two tools can produce the same passing output with very different risk profiles. One may make a narrow patch. Another may rewrite half the module and pass by accident.

A useful comparison looks at five signals. First, did the assistant identify the failing behavior before editing? Second, did it keep changes close to the affected boundary? Third, did it explain what it changed in terms a maintainer can verify? Fourth, did it run the smallest meaningful test? Fifth, did it avoid hidden churn such as formatting, dependency changes, or broad renames?

Also compare recovery behavior. Good coding tools handle surprises well: dirty worktrees, flaky tests, missing dependencies, ambiguous user requests, and partial failures. If a tool can pass a clean demo but struggles when the environment is messy, it may not be the better daily tool.

For team use, record the review burden. If one assistant passes tests but produces changes that require long human review, the saved time may disappear. If another produces smaller diffs and clearer evidence, it may be more valuable even when both appear equal on a benchmark.

The practical evaluation question is: which assistant leaves the next maintainer more confident, not which one reached green first.

How to compare coding assistants when both can pass the same test

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