Test coverage gaps: diagnostics lifecycle, save-flush, image-path, nested properties

Summary

Several editor features lack automated test coverage, including the diagnostics lifecycle, save-flush debounce, and image-path resolution flows.

Details

Diagnostics lifecycle (diagnostics-provider.ts:26-115)

The event-driven diagnostics lifecycle (onDidOpenTextDocument, debounced onDidChangeTextDocument, configuration refresh, close cleanup) is untested beyond source-text regex checks. Need tests that edit a manifest and verify Problems updates, toggle settings, and confirm close clears diagnostics.

Save-flush path (manifest-editor-provider.ts:182-241)

The Ctrl+S flush path for debounced webview edits (flushChanges/changesFlushed nonce-based handling with 500ms timeout) has no coverage. Need E2E test that types and immediately saves without waiting out debounce.

Image-path resolution (manifest-editor-provider.ts:248-342)

checkImagePath and copyToAssets flows are untested despite multiple branches: in-package hits, workspace fallback, absolute/external files, notFound, and duplicate-name collision renaming.

Nested Properties round-trip (manifest-parser.ts:249-291)

PackageIntegrity, AutoUpdate, and UpdateWhileInUse fields lack round-trip parse/save test coverage.

Recommendation

Add targeted extension-host and E2E tests for each of these flows.

Surfaced by PR review skill (test-coverage dimension)