Conciseness

The body is short and mostly efficient, but step 2 ("error paths, boundary conditions, null/empty inputs") and step 4 ("Error handling and exceptions; Boundary values (min/max, empty, null); Edge cases and corner cases") duplicate each other, and the framework list ("Jest/Vitest/Mocha", "pytest/unittest", "Go testing/testify", "Rust test framework") enumerates knowledge Claude already has. This matches anchor 3 ("could be tightened"); it is not 2 because there is no padding, and not 4 because the duplication spans two full steps, beyond a minor trim.

Actionability

Steps and scenario targets are concrete ("Run coverage report to identify untested branches", "Boundary values (min/max, empty, null)"), but there are no executable commands — no coverage invocation like `pytest --cov` or `npx jest --coverage` — and no example test. This matches anchor 3 ("Some concrete guidance but incomplete; missing key details"); it is not 4 because no commands or code appear at all, and not 2 because the sequence and targets are specific rather than high-level hints.

Workflow Clarity

The five-step sequence is clear and ends with an explicit verification checkpoint ("Verify improvement: Run coverage again, confirm measurable increase"). This matches anchor 4 ("Clear sequence with most checkpoints present; minor validation gaps"); it is not 5 because there is no feedback loop — the workflow never instructs running the new tests and fixing failures — and not 3 because validation is explicit rather than implicit.

Progressive Disclosure

The skill is under 50 lines with no bundle files and no need for external references, and content is organized into an intro and a "## Command Template" section. It matches anchor 4 rather than the simple-skill 5 case because of minor organization gaps: a stray "# Expand Unit Tests" H1 appears nested after the H2 section, and the trailing instruction ("Present new test code blocks only...") sits outside any section.

Specificity

The description names the domain and 1-2 concrete actions — "Increase test coverage by targeting untested branches and edge cases" — but is not comprehensive, omitting writing tests, analyzing coverage reports, or frameworks. It matches anchor 3; it is not 4 because it lists fewer distinct actions than "Extracts text from PDF files, fills forms, converts pages to images", and not 2 because the actions are concrete rather than generic.

Completeness

The description has a clear "what" ("Increase test coverage by targeting untested branches and edge cases") but no "when" — there is no "Use when..." clause or equivalent trigger guidance, which caps completeness at 3 per the rubric guideline. It cannot be 4 because anchor 4 requires both what and when.

Trigger Term Quality

Natural keywords are present ("test coverage", "untested branches", "edge cases") but common variations are missing — notably the central term "unit tests" itself, plus "code coverage" and "write more tests". This matches anchor 3 ("Some relevant keywords but missing common variations or synonyms"); it falls short of anchor 4 because the skill's core keyword is absent.

Distinctiveness Conflict Risk

"untested branches and edge cases" carves a fairly specific testing niche that is mostly distinct, with only minor overlap risk against general test-writing or TDD skills. It matches anchor 4; it is not 5 because no explicit trigger phrases fully separate it from sibling testing skills, and not 3 because it is considerably more specific than "Works with document files".