DocsReferencePrs

Production Readiness Score (PRS)

PRS is Quell's measure of edge-case test quality. It's not coverage — it's a measure of whether your tests actually catch bugs.

The formula

PRS = (WRITTEN × 1.0 + SCAFFOLDED × 0.5) / total_requirements × 100

Weighted by how well each bucket catches bugs:

  • WRITTEN counts fully — gate 5 proved the test catches violations
  • SCAFFOLDED counts half — structure is correct, but not fully proven
  • FLAGGED counts zero — documented but not testable

Score tiers

ScoreTierMeaning
80–100Production ReadyEdge cases are well-covered
60–79Review NeededSignificant gaps remain
0–59Needs WorkMany untested edge cases

Why PRS vs coverage

A codebase with 91% line coverage might have a PRS of 52.

Both numbers are correct. They measure different things.

Coverage tells you which lines ran during your test suite. PRS tells you whether tests would catch a real bug in those lines.

You can have 100% coverage with zero PRS if all your tests just assert the function returns something without checking correctness.

Improving your PRS

quell find src/ --fix    # write tests for verified gaps
quell score src/         # see current PRS by file

The fastest wins are usually:

  1. Functions with explicit Raises in their docstrings
  2. Pydantic models with field validators
  3. Functions with guard clauses at the top

PRS in CI

Enforce a minimum score on every PR:

quell ci src/ --threshold 75

See CI/CD Integration for setup details.