Overview

Follow-up to #197 (Phase 1 unit tests). These tests address gaps discovered during Phase 1 implementation and focus on integration points and edge cases that can still run headless in CI.

Target: v3000.0.x

New Test Suites

1. Notification/Observer Integration Tests

Test that components respond correctly to preference changes (not just that preferences persist):

- testRendererRespondsToStyleChange       // MPRenderer updates when theme changes
- testHighlighterRespondsToFontChange     // Editor re-highlights on font change
- testPreferenceChangeCoalescence         // Rapid changes don't cause thrashing
- testThemeChangeNotification             // Verify observers receive theme changes
- testFontSizeChangeNotification          // Font changes propagate correctly

Approach:

• Register mock observers for NSNotificationCenter
• Trigger preference changes
• Verify callbacks fire with correct data
• Test that dependent components update state

2. MPDocument Lifecycle Tests

Test document state management beyond basic I/O:

- testDocumentDirtyFlagAfterEdit
- testDocumentRevertToSaved
- testDocumentEncodingDetection           // Auto-detect UTF-8 vs Latin-1
- testDocumentWithNoExtension
- testSaveWithFileConflict                // File modified externally
- testOpenFileDeletedDuringEdit           // File removed while open

Approach:

• Create MPDocument instances programmatically
• Manipulate document state
• Verify flags and behaviors

3. Renderer Edge Cases

Additional renderer scenarios discovered during Phase 1:

- testRendererWithNilDataSource
- testRendererWithEmptyMarkdown
- testRendererExtensionCombinations       // Tables + footnotes + strikethrough
- testRendererWithMalformedHTMLInCodeBlocks
- testRenderCancellation
- testConcurrentRenderRequests

4. HGMarkdownHighlighter Coverage Gaps

The highlighter has 75% coverage but some paths are untested:

- testHighlighterWithLargeDocument        // Performance/stress test
- testHighlighterStyleParsingErrors       // Error callback (0% covered)
- testHighlighterTextViewDidChange        // 0% covered currently
- testHighlighterScrollHandler            // Partial coverage

5. Image Handling in Exports

- testExportWithEmbeddedImages            // Base64 images render correctly
- testExportWithLinkedImages              // External image URLs preserved
- testInvalidImageURLs                    // Graceful handling of broken images

Out of Scope (Requires GUI)

• PDF export (needs print subsystem)
• Clipboard operations (needs pasteboard)
• Live preview synchronization (needs WebView display)
• Autosave (tightly coupled to AppKit)

Success Criteria

• All new tests pass
• Tests run headless in CI
• No flaky tests
• Coverage improvement measurable (target: 50%+ overall)

Priority

1. High: Notification/observer tests - this is where integration bugs hide
2. Medium: Document lifecycle tests
3. Medium: Renderer edge cases
4. Lower: Highlighter gaps (already decent coverage)

Related

• Test Coverage Phase 1: Enhanced Unit Tests #197 - Phase 1 unit tests (complete)
• PR Address issue #197: Test Coverage Phase 1 - Enhanced Unit Tests #233 - Phase 1 implementation
• plans/xcuitest.md - Full technical design