Agent Skills › JamieMason/syncpack › testing-gaps

testing-gaps

GitHub

分析指定源文件的测试覆盖率，识别未覆盖的代码分支及缺失的真实场景。通过运行文本格式覆盖率报告，定位零执行次数的行，结合测试文件交叉验证，分类处理未覆盖路径并报告遗漏的组合测试用例。

.claude/skills/testing-gaps/SKILL.md JamieMason/syncpack

Trigger Scenarios

需要分析代码测试覆盖率寻找未被测试的分支逻辑发现潜在的死代码或防御性分支

Install

npx skills add JamieMason/syncpack --skill testing-gaps -g -y

More Options

Non-standard path

npx skills add https://github.com/JamieMason/syncpack/tree/main/.claude/skills/testing-gaps -g -y

Use without installing

npx skills use JamieMason/syncpack@testing-gaps

指定 Agent (Claude Code)

npx skills add JamieMason/syncpack --skill testing-gaps -a claude-code -g -y

安装 repo 全部 skill

npx skills add JamieMason/syncpack --all -g -y

预览 repo 内 skill

npx skills add JamieMason/syncpack --list

SKILL.md

Frontmatter

{
    "name": "testing-gaps",
    "description": "Run coverage, inspect results, and identify missing test scenarios for a given source file. Use when analysing test coverage or finding untested branches."
}

Testing Gaps

Find untested branches and missing real-world test scenarios for a source file.

Workflow

Run text coverage for the target file
Identify uncovered branches from the output
Cross-reference with test file to understand what's tested
Report uncovered branches + missing real-world scenarios

Step 1: Run Coverage

Use cargo llvm-cov with --text output (not --html) for parseable results.

# Full coverage, filtered to target file
cargo llvm-cov test --text \
  --ignore-run-fail \
  --ignore-filename-regex '(_test.rs|\/test\/)' \
  2>/dev/null | sed -n '/TARGET_FILE\.rs:/,/^$/p'

Example for preferred_semver.rs:

cargo llvm-cov test --text \
  --ignore-run-fail \
  --ignore-filename-regex '(_test.rs|\/test\/)' \
  2>/dev/null | sed -n '/preferred_semver\.rs:/,/^$/p'

Step 2: Read Coverage Output

The text format shows per-line execution counts:

  42|     80|        .and_then(|range| ...)     # Hit 80 times
  74|      0|        Some(preferred)            # Never hit
 321|      0|        instance.mark_conflict(...) # Never hit

count > 0 = covered
count = 0 = uncovered branch
^N annotations on sub-expressions show partial coverage within a line

Extract only uncovered lines

... | grep -E '^\s+\d+\|\s+0\|'

Step 3: Classify Gaps

For each uncovered branch, determine:

What code path leads here? — Trace the if/else chain backward
What input would trigger it? — What package.json + config combination
Is it reachable? — Some branches may be defensive/unreachable
Is it worth testing? — Real-world scenario vs theoretical edge case

Category	Action
Real-world scenario never tested	Write a test
Edge case in existing logic	Write a test
Defensive branch (unreachable)	Note but skip
Dead code	Consider removing

Step 4: Identify Missing Scenarios

Beyond line coverage, look for missing combinations:

Feature A tested, Feature B tested, A+B never tested together
Only tested with one package, never with multiple
Only tested with highestSemver, never lowestSemver
Only tested with one range type (^), never others (>=, <=)
Only tested without semver groups, never with

Step 5: Report

Structure findings as:

Uncovered branches — Specific lines, what triggers them, why untested
Missing real-world scenarios — Combinations and interactions not covered

Running Tests After Adding Coverage

just test                              # All tests
cargo test test_name -- --nocapture   # Specific test
just coverage                         # Regenerate coverage report