[nightshift] test-gap: 54 of 61 source files have zero test coverage (~4.7% test-to-code ratio)

[nightshift-micr]

Test Coverage Gap Analysis — micr-dev/blog

Executive Summary

Metric	Value
Source files (non-test, non-type-decl)	61 files (~4,554 LOC)
Test files	3 files (212 LOC)
Tests	12 passing
Test framework	Vitest 4.1 (node environment)
Test-to-code ratio	~4.7% by LOC
Modules with any test coverage	5 of 61 files (~8%)
Estimated functional coverage	~15-20% of pure-logic code

Files WITH Tests

Source File	Test File	What's Tested
src/lib/post-parser.ts	src/lib/posts.test.ts	parseEditablePost, default merging, frontmatter parsing
src/lib/posts.ts	src/lib/posts.test.ts	slugifyTag
src/lib/mdx.tsx	src/lib/mdx.test.ts	renderMdx (shortcodes, mermaid fallback, ascii fences), getFontStyleSheet, getThemeStyle
src/lib/mermaid-ascii.ts	src/lib/mdx.test.ts	renderMermaidAscii (flowcharts, sequences)
src/lib/share-links.ts	src/lib/share-links.test.ts	buildShareHref (x, bluesky, linkedin)

Files WITHOUT Tests

54 source files have zero test coverage, including all React components, all route pages, the API proxy, and several utility modules.

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Critical Test Gaps

P0 — High Severity

1. src/lib/post-parser.ts — Zod validation edge cases

• Gap: Only happy-path parsing tested. No tests for missing frontmatter, invalid YAML, malformed dates, empty required fields.
• Recommended tests: Missing --- delimiters, invalid YAML, empty title/date/excerpt, non-date strings for date, missing optional fields.
• Effort: 2–3 hours

2. src/lib/posts.ts — Post loading, tag aggregation, adjacent posts

• Gap: Only slugifyTag tested. Critical functions untested: getPostBySlug, getPostIndex, getTags, getPostsByTag, getAdjacentPosts, formatDate.
• Recommended tests: formatDate() edge cases, getAdjacentPosts() first/last/empty, getTags() dedup/count, getPostBySlug() null returns.
• Effort: 3–4 hours

3. src/lib/mermaid-ascii.ts — Parser edge cases

• Gap: Only simple flowchart/sequence tested. Complex regex logic with many untested branches.
• Recommended tests: Empty input, edge labels, different arrow types, node shapes, unknown diagram types, malformed lines.
• Effort: 2–3 hours

P1 — Medium-High Severity

4. src/lib/mdx.tsx — MDX component rendering edge cases

• Gap: Happy paths only. Many getMdxComponents branches untested.
• Effort: 3–4 hours

5. src/lib/og.tsx — OG image layout calculations

• Gap: Pure functions getOgTitleStyle, getScytheFrame, getOgPreviewTheme completely untested.
• Effort: 1–2 hours

6. src/lib/og-assets.ts — SVG manipulation

• Gap: tintSvg, cropScytheSvg, svgToDataUri are pure functions that could be tested.
• Effort: 1 hour

P2 — Medium Severity

7. src/components/search-page.tsx (169 LOC) — Search functionality

• Gap: Largest component with zero tests. Extract search/filter logic into pure utility for testing.
• Effort: 2–3 hours

8. src/components/local-editor.tsx (305 LOC) — MDX editor

• Gap: Largest file, completely untested. Contains file-system access and editor state management.
• Effort: 3–4 hours

9. src/app/sitemap.ts — Sitemap generation

• Gap: No tests verify correct URL structure.
• Effort: 1 hour

10. src/app/api/agentation/[...path]/route.ts — API proxy

• Gap: Request forwarding, header stripping, dev-only guard untested.
• Effort: 1–2 hours

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Recommendations

Immediate Actions

1. Add coverage reporting — Add "test:coverage": "vitest run --coverage" and install @vitest/coverage-v8.
2. Expand post-parser.ts tests — Zod schema validation is the most critical safety net. Malformed frontmatter could crash the blog.
3. Test posts.ts functions — Mock filesystem and test all exported functions.
4. Expand mermaid-ascii.ts tests — Many regex patterns need edge case coverage.

Configuration Improvements

5. Enable *.test.tsx — vitest config include should be ["src/**/*.test.{ts,tsx}"].
6. Add jsdom environment for component tests — @testing-library/react requires DOM.

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