Systematic test coverage expansion: 13% → 55-60%

[smithrashell]

Context

Overall Jest test coverage is 13.5% (50 test files, 793 tests). Core services like problemService (79%) and sessionService (73%) are decent, but huge gaps exist:

• 20 of 24 DB store files have zero tests
• 8 of 9 problem service files are untested (including files modified for the enrichment fix in bug: Hints used card on Overview page not reflecting accurate data #247)
• Schedule/recalibration services — the spaced repetition engine — are at 0-3%
• Retry/resilience layer is essentially untested

Target: 55-60% overall, with 75%+ on critical business logic.

Scope: Jest unit tests only. The browser integration tests (core-business-tests.js) are complementary and remain unchanged.

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Phase 1 — Critical Algorithms (13% → 25-28%)

Locks down the session assembly pipeline, enrichment fix, normalizer, and schedule service.

1.1 problemNormalizerHelpers.test.js (~14 tests)

Source: src/shared/services/problem/problemNormalizerHelpers.js (93 lines, ~0%) → target 90%

• Pure functions, no mocks needed
• buildSessionMetadata, buildAttemptTracking, buildSpacedRepetitionData, buildAttemptsArray, etc.

1.2 problemServiceHelpers.test.js (~28 tests)

Source: src/shared/services/problem/problemServiceHelpers.js (127 lines, 21%) → target 85%

• enrichReviewProblem — validates the enrichment fix from the difficulty crash
• normalizeReviewProblem — slug fallback chain, attempt_stats conversion
• filterValidReviewProblems — validates required fields

1.3 problemNormalizer.test.js (~24 tests)

Source: src/shared/services/problem/problemNormalizer.js (221 lines, 61%) → target 85%

• validateRawProblem — missing difficulty (the bug), missing tags, non-numeric id
• normalizeProblem — id coercion, title case, metadata flags
• normalizeProblems — array validation, error wrapping with index

1.4 scheduleService.test.js (~20 tests)

Source: src/shared/services/schedule/scheduleService.js (138 lines, 3%) → target 70%

• isDueForReview — date boundaries
• isRecentlyAttempted — box-level skip intervals, relaxation
• getDailyReviewSchedule — sorting, limits, error handling

1.5 problemServiceSession.test.js (~50 tests)

Source: src/shared/services/problem/problemServiceSession.js (590 lines, 45%) → target 80%

• addTriggeredReviewsToSession — validates enrichment fix, max 2 per session
• addFallbackProblems — validates enrichment + difficulty/tags filtering fix
• addReviewProblemsToSession, addNewProblemsToSession, addPassiveMasteredReviews
• deduplicateById, problemSortingCriteria

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Phase 2 — Data Layer & Resilience (25-28% → 38-42%)

2.1 problems.test.js (~25 tests) — src/shared/db/stores/problems.js

2.2 standard_problems.test.js (~15 tests) — src/shared/db/stores/standard_problems.js

2.3 tag_mastery.test.js (~22 tests) — src/shared/db/stores/tag_mastery.js

2.4 attempts.test.js (~16 tests) — src/shared/db/stores/attempts.js

2.5 storageService.enhanced.test.js (~22 tests) — src/shared/services/storage/storageService.js (12% → 60%)

2.6 indexedDBRetryService.test.js (~25 tests) — circuit breaker, exponential backoff, abort controller

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Phase 3 — Session Features (38-42% → 48-53%)

3.1 recalibrationService.test.js (~30 tests) — decay logic, diagnostic sessions, welcome-back strategy

3.2 sessionHabitLearning.test.js (~25 tests) — streaks, cadence, circuit breaker

3.3 interviewService.test.js (~28 tests) — mode configs, readiness assessment, transfer metrics

3.4 problemServiceRetry.test.js (~18 tests) — retry wrappers, abort controller cancellation

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Phase 4 — Monitoring & Infrastructure (48-53% → 55-60%)

4.1 recalibrationHelpers.test.js (~12 tests)

4.2 crashReporter.test.js (~10 tests)

4.3 ErrorReportService.test.js (~10 tests)

4.4 PerformanceMonitor.test.js (~10 tests)

4.5 logger.test.js (~8 tests)

4.6 problem_relationships.enhanced.test.js (~12 tests)

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Coverage Projection

Phase	New Files	New Tests	Cumulative Coverage
Phase 1	5	~136	25-28%
Phase 2	6	~125	38-42%
Phase 3	4	~101	48-53%
Phase 4	6	~62	55-60%
Total	21	~424	55-60%

Shared Infrastructure

• Extend mockDataFactories.js with createMockReviewProblem, createMockStandardProblem, createMockAttemptWithStats
• Create dbTestHelper.js in Phase 2 for fake-indexeddb schema setup and seeding

Implementation Order (Phase 1)

1. problemNormalizerHelpers.test.js — pure functions, zero mocks, fast start
2. problemServiceHelpers.test.js — validates enrichment fix
3. problemNormalizer.test.js — validates the validation layer
4. scheduleService.test.js — small file, pure scheduling logic
5. problemServiceSession.test.js — largest, depends on understanding helpers

Verification

After each phase:

1. npm run test:coverage — confirm cumulative coverage meets phase target
2. npm test — all existing + new tests pass
3. Verify no cross-phase test dependencies