coverage-improvement

name	coverage-improvement
description	Guide systematic coverage improvement using vitest-agent MCP tools. Use when improving code coverage, targeting uncovered lines, or working toward coverage targets.

Improving Code Coverage

Systematic approach to identifying and covering untested code using MCP tools.

Step 1: Identify Coverage Gaps

Use test_coverage to see project-wide coverage gaps:

• Files below threshold with exact uncovered line ranges
• Per-metric values (statements, branches, functions, lines)
• Current thresholds and targets

For a specific file, use file_coverage({ filePath: "src/foo.ts" }) to get per-metric values and uncovered line ranges.

Step 2: Understand Existing Tests

Use test_for_file({ filePath: "src/foo.ts" }) to find which test files already cover the source file. Then use test_get({ fullName: "Suite > test name" }) to understand individual test scope and history.

Step 3: Write Targeted Tests

Focus on the uncovered lines from step 1:

1. Read the source file at the uncovered line ranges
2. Identify untested code paths (branches, error handlers, edge cases)
3. Write tests targeting those specific paths
4. Run with run_tests({ files: ["path/to/test.ts"] })

Step 4: Verify Improvement

1. Use file_coverage to check the file's updated coverage
2. Use test_coverage to verify project-wide improvement
3. Use test_trends to confirm coverage direction is improving

Prioritization

Focus on files with the largest coverage gaps first. Files near the threshold ("at-risk" files) are the highest priority since a small regression could push them below the threshold.

Recording Progress

Use note_create to document:

• Which files you improved and by how much
• Untested paths that were intentionally deferred
• Coverage targets agreed upon with the team