lcov

Testing & Quality

LCOV tooling - finding gaps, parsing coverage files, marker syntax

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How to use this skill

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I want to install this Agent Skill for this project in Codex.

Source SKILL.md: https://github.com/majiayu000/claude-skill-registry/blob/HEAD/skills/testing/lcov/SKILL.md

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LCOV Tooling

Finding Coverage Gaps

# Run coverage first
make check-coverage

# Uncovered lines
grep "^DA:" reports/coverage/coverage.info | grep ",0quot;

# Uncovered branches
grep "^BRDA:" reports/coverage/coverage.info | grep ",0quot;

# Uncovered functions
grep "^FNDA:0," reports/coverage/coverage.info

coverage.info Format

SF:/path/to/file.c          # Source file
FN:42,function_name         # Function at line 42
FNDA:5,function_name        # Function called 5 times
DA:45,3                     # Line 45 executed 3 times
DA:46,0                     # Line 46 never executed (GAP!)
BRDA:50,0,0,2               # Line 50, block 0, branch 0, taken 2 times
BRDA:50,0,1,0               # Line 50, block 0, branch 1, never taken (GAP!)
end_of_record

Key patterns:

DA:line,0 = uncovered line
BRDA:line,block,branch,0 = uncovered branch
FNDA:0,name = uncovered function

Coverage Files

Command	Output
`make check-coverage`	`reports/coverage/coverage.info`, `reports/coverage/summary.txt`
`make check-coverage TEST=unit/foo`	`reports/coverage/unit/foo.coverage.info`, `.coverage.txt`

Exclusion Markers

Marker	Effect
`LCOV_EXCL_LINE`	Exclude entire line
`LCOV_EXCL_BR_LINE`	Exclude branch only
`LCOV_EXCL_START` / `LCOV_EXCL_STOP`	Block exclusion (wrapper.c only)

Usage:

assert(ptr != NULL);                    // LCOV_EXCL_BR_LINE
if (!ptr) PANIC("Invariant violated");  // LCOV_EXCL_BR_LINE

Note: Markers are NOT reliably honored inside static functions. Inline code instead.

See coverage skill for exclusion policy (what's allowed vs forbidden).

Quick Workflow

# 1. Run coverage
make check-coverage

# 2. Check summary
cat reports/coverage/summary.txt

# 3. Find gaps in specific file
grep -A 1000 "SF:.*myfile.c" reports/coverage/coverage.info | \
  grep -m 1 -B 1000 "end_of_record" | grep ",0quot;

Related Skills

coverage - Policy (100% requirement, exclusion rules)
testability - Refactoring patterns for gaps