Coverage Gap Analyzer

Identify files with missing or insufficient test coverage.

Usage

/coverage-gaps [threshold] - Find files below coverage threshold (default: 50%)

Instructions

When invoked, follow these steps:

Step 1: Detect Test Framework

Check for these configuration files to identify the test framework:

ls -la jest.config.* vitest.config.* pytest.ini pyproject.toml setup.cfg karma.conf.* .rspec phpunit.xml go.mod Cargo.toml 2>/dev/null

Config File	Framework	Test Pattern
jest.config.*	Jest (JS/TS)	*.test.ts, *.spec.ts, __tests__/
vitest.config.*	Vitest (JS/TS)	*.test.ts, *.spec.ts
pytest.ini, pyproject.toml	Pytest (Python)	test_*.py, *_test.py
go.mod	Go testing	*_test.go
Cargo.toml	Rust	tests/, #[test] in source
.rspec	RSpec (Ruby)	*_spec.rb
phpunit.xml	PHPUnit	*Test.php

Step 2: Find Existing Coverage Reports

Look for coverage output in common locations:

find . -maxdepth 3 -type f \( -name "lcov.info" -o -name "coverage.xml" -o -name "cobertura.xml" -o -name ".coverage" -o -name "coverage.json" \) 2>/dev/null

Also check directories:

ls -d coverage/ .nyc_output/ htmlcov/ target/coverage/ 2>/dev/null

Step 3: Analyze Coverage

Option A: Parse Existing Coverage Report

If an lcov.info file exists, parse it:

grep -E "^SF:|^LH:|^LF:" coverage/lcov.info | paste - - - | awk -F'[:|]' '{file=$2; hit=$4; total=$6; pct=(total>0)?hit/total*100:0; if(pct<THRESHOLD) print pct"% - "file}' | sort -n

If coverage.xml (Cobertura) exists:

grep -E 'filename=|line-rate=' coverage.xml | paste - - | awk '{...}'

Option B: Map Source Files to Tests (No Coverage Report)

Find source files:

find src lib app -type f \( -name "*.ts" -o -name "*.js" -o -name "*.py" -o -name "*.go" -o -name "*.rb" \) 2>/dev/null | grep -v -E "(test|spec|__test__|_test)"

Find test files:

find . -type f \( -name "*.test.*" -o -name "*.spec.*" -o -name "test_*" -o -name "*_test.*" \) 2>/dev/null

Map each source file to potential test files by name convention:

• src/utils/auth.ts → src/utils/auth.test.ts or tests/utils/auth.test.ts
• lib/payments.py → tests/test_payments.py or lib/test_payments.py

Step 4: Get File Metadata

For files with gaps, gather additional context:

wc -l <file>                           # Line count
git log -1 --format="%ar" -- <file>    # Last modified
git log --oneline -- <file> | wc -l    # Commit frequency

Step 5: Format Report

Present gaps in this format:

COVERAGE GAPS (threshold: {threshold}%)

No tests found:
• src/utils/validation.ts (247 lines, modified 3 days ago)
• src/api/payments.ts (189 lines, modified today) ⚠️

Low coverage (<{threshold}%):
• src/auth/oauth.ts — 34% covered
• src/db/migrations.ts — 12% covered

Summary:
─────────────────────────────
Files with no tests:     12
Files below threshold:    5
Total files analyzed:    87
─────────────────────────────

Suggestion: Start with {highest_priority_file} ({reason})

Step 6: Prioritization Logic

Rank files by priority using this scoring:

1. Recently modified (+3 points if modified in last 7 days)
2. Large file (+2 points if >200 lines)
3. High commit frequency (+2 points if >10 commits)
4. Critical path (+3 points if contains: auth, payment, security, user)

Suggest the highest-scored file first.

Example Output

COVERAGE GAPS (threshold: 50%)

No tests found:
• src/utils/validation.ts (247 lines, modified 3 days ago)
• src/api/payments.ts (189 lines, modified today) ⚠️
• src/helpers/format.ts (45 lines, modified 2 weeks ago)

Low coverage (<50%):
• src/auth/oauth.ts — 34% covered
• src/db/migrations.ts — 12% covered

Summary:
─────────────────────────────
Files with no tests:      3
Files below threshold:    2
Total files analyzed:    28
─────────────────────────────

Suggestion: Start with src/api/payments.ts (recently modified + no tests + critical path)

Fallback Behavior

• If no test framework detected: "No test framework found. Looking for source files without corresponding test files..."
• If no coverage report exists: "No coverage report found. Run your test suite with coverage enabled, or I'll analyze by file naming convention."
• If codebase is empty or no source files: "No source files found in standard directories (src/, lib/, app/)"

Tips for Users

After running this command, you can ask:

• "Generate a test file for src/api/payments.ts"
• "What should I test first in oauth.ts?"
• "Create a coverage improvement plan"