test-coverage-analyzer

Purpose

Find the testing gaps that actually matter — untested behaviors weighted by risk — instead of chasing a line-coverage percentage that can be high while the important paths remain unverified.

When to Use

• Deciding where to invest limited testing effort next.
• Coverage numbers look acceptable but bugs keep escaping to production.
• Before modifying risky code, to find out what's currently protecting it (and what isn't).

Differs from Test Generator: that writes tests; this decides which tests are worth writing first.

What to Analyze

1. Untested behaviors, not untested lines — a line executed by a test that asserts nothing is covered on paper and untested in reality. Look for assertions, not execution.
2. Risk-weight each gap — an untested path handling money, auth, data deletion, or external input matters far more than an untested display formatter. Rank accordingly.
3. Error and failure paths — these are the most commonly untested and the most likely to be wrong, precisely because they're rarely exercised manually.
4. Boundary and edge conditions — even where a happy path is tested, check whether empty/zero/max/null cases are (pair with Edge Case Hunter to enumerate them).
5. Tests that would pass even if the code broke — tautological assertions, over-mocked tests that only verify the mock, snapshot tests nobody reviews. These create false confidence, which is worse than a known gap.
6. Change frequency — frequently-modified code benefits more from tests than stable code that hasn't changed in two years.

Output Format

• Risk-ranked gap list — each with: what's untested, why it matters (the concrete failure it would allow), and the test that would close it.
• False-confidence findings — existing tests that don't actually verify what they appear to, called out separately since they're more dangerous than plain gaps.
• Deliberately low priority — areas not worth testing heavily right now, and why.

Avoid

• Reporting or recommending a coverage percentage target as the goal — high coverage with weak assertions is a common and misleading outcome.
• Treating all uncovered code as equally important.
• Recommending tests for stable, low-risk code just to raise a number.