code-coverage

name	code-coverage
description	Analyzes test coverage, identifies untested code paths, and generates tests for the most critical uncovered areas. Use to improve test coverage before releases.
argument-hint	[file, module, or 'all']
allowed-tools	Read, Grep, Glob, Bash, Write

Test Coverage Analysis

Detect Test Setup

!ls package.json jest.config.* vitest.config.* .nycrc* .c8rc* .coveragerc* setup.cfg pyproject.toml tox.ini 2>/dev/null !cat package.json 2>/dev/null | grep -E "jest|vitest|c8|nyc|istanbul|coverage" | head -5

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Process

Step 1: Run Coverage (if configured)

Attempt to run the project's coverage command:

Ecosystem	Coverage Command
npm (Jest)	npx jest --coverage --json 2>/dev/null
npm (Vitest)	npx vitest run --coverage 2>/dev/null
npm (c8)	npx c8 report --reporter=json 2>/dev/null
Python (pytest)	python -m pytest --cov --cov-report=json 2>/dev/null
Go	go test -coverprofile=coverage.out ./... 2>/dev/null && go tool cover -func=coverage.out
Rust	cargo tarpaulin --out json 2>/dev/null

If coverage tools aren't configured, proceed with static analysis.

Step 2: Static Analysis (if no coverage tool)

For the target file(s):

1. Identify all public functions, methods, and classes
2. Search for corresponding test files
3. For each function, check if there's a test that calls it
4. Map which code paths (branches, error handlers) have test coverage

Step 3: Coverage Report

Summary

Metric	Value
Line coverage	XX%
Branch coverage	XX%
Function coverage	XX%
Uncovered files	X

Uncovered Critical Code

List the most important uncovered code, prioritized by:

1. Business logic — core features and workflows
2. Error handling — catch blocks, error paths, edge cases
3. Security-sensitive — auth, input validation, data access
4. Complex logic — functions with high cyclomatic complexity

For each uncovered area:

• File path and line numbers
• What the code does
• Why it's important to test
• Suggested test cases

Step 4: Generate Missing Tests

For the top 5 most critical uncovered areas, generate test code following the project's test patterns (same structure as /write-tests).

Step 5: Coverage Improvement Plan

Priority	File	Current	Target	Tests Needed
1	...	XX%	80%+	...
2	...	XX%	80%+	...

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Rules

• Focus on meaningful coverage, not 100% — test behavior, not implementation
• Prioritize business logic and error paths over boilerplate
• Don't generate tests just to increase numbers — each test should validate something valuable
• Respect existing test patterns and conventions