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+# TDD Test Rewrite Design
+
+## Goal
+
+Delete all existing tests and rewrite using true TDD methodology (specification-first + property-based) to surface logic bugs in the implementation. Document expected behavior for every tested function.
+
+## Methodology
+
+### Specification-First + Property-Based TDD
+
+- **Specification-First**: Define expected behavior from requirements/intent, not current implementation
+- **Property-Based**: Define invariants that must always hold regardless of input
+- **Document-First**: Add input/output comments to source functions before writing tests
+
+### The Process
+
+1. **Read** - Examine function, callers, and context to understand intent
+2. **Document** - Add `/// - Expected:` comment block to source file
+3. **Test** - Write tests that verify documented expectations
+4. **Batch Run** - Run all tests at the end
+5. **Fix** - Failures indicate logic bugs; fix implementation to match expectations
+
+## Documentation Standard
+
+Every tested function gets this comment format:
+
+```swift
+/// Calculates optimal routes between game locations.
+///
+/// - Parameter games: List of games to route between (must be chronologically sorted)
+/// - Parameter maxDailyMiles: Maximum driving distance per day (default: 500)
+/// - Returns: Array of valid routes, each containing sequential games
+///
+/// - Expected Behavior:
+///   - Empty input → returns empty array
+///   - Single game → returns array with one single-game route
+///   - Games on same day in distant cities → excludes impossible transitions
+///   - Routes respect maxDailyMiles constraint
+///   - Routes are chronologically ordered
+///
+/// - Invariants:
+///   - All returned routes have games in chronological order
+///   - No route exceeds maxDailyMiles between consecutive same-day games
+func findRoutes(games: [Game], maxDailyMiles: Int = 500) -> [[Game]]
+```
+
+## Test Structure
+
+Each test file has three sections:
+
+```swift
+@Suite("ComponentName")
+struct ComponentNameTests {
+
+    // MARK: - Specification Tests
+    // Tests derived from "Expected Behavior" comments
+
+    // MARK: - Property Tests
+    // Tests that verify invariants for any input
+
+    // MARK: - Edge Case Tests
+    // Boundary conditions and unusual inputs
+}
+```
+
+### Property-Based Patterns
+
+| Pattern | Example | Applies To |
+|---------|---------|------------|
+| Idempotency | `filter(filter(x)) == filter(x)` | RouteFilters |
+| Roundtrip | `decode(encode(x)) == x` | All Codable models |
+| Ordering | Routes always chronological | GameDAGRouter |
+| Bounds | Distance ≤ maxDailyMiles | TravelEstimator |
+| Conservation | Total games in = total games out | ItineraryBuilder |
+
+## Execution Phases
+
+### Phase 1: Delete & Infrastructure (~15 min)
+- Delete all 53 existing test files
+- Create `TestFixtures.swift` with factories
+- Create `MockServices.swift` with test doubles
+
+### Phase 2: Planning Engine (~2-3 hours)
+Document + test in dependency order:
+1. `TravelEstimator` (no dependencies)
+2. `RouteFilters` (no dependencies)
+3. `PlanningModels` (data structures)
+4. `GameDAGRouter` (uses TravelEstimator)
+5. `ItineraryBuilder` (uses filters)
+6. `ScenarioPlanner` + A/B/C/D variants
+7. `TripPlanningEngine` (orchestrator)
+
+### Phase 3: Domain Models (~1.5-2 hours)
+15 files: Game, Trip, Stadium, Team, Sport, Region, Division, TripStop, TravelSegment, TripPreferences, Progress, DynamicSport, TripPoll, AnySport, AchievementDefinitions
+
+Focus: Codable roundtrips, computed properties, classification logic
+
+### Phase 4: Services (~2-3 hours)
+23 files covering:
+- Error enums (CloudKitError, SyncError, etc.)
+- Result types (SyncResult, ScoreResolutionResult)
+- Configuration states (unconfigured, invalid)
+- Rate limiting, caching, network states
+
+### Phase 5: Export (~30 min)
+2 files: ShareableContent types, POISearchService types
+
+### Phase 6: Run & Fix (~1-2 hours)
+- Run full test suite
+- Failures = logic bugs in implementation
+- Fix source code to match documented expectations
+- If expectation was wrong, discuss and adjust
+
+## Bug Handling
+
+| Situation | Action |
+|-----------|--------|
+| Implementation bug | Fix source code to match documented expectation |
+| Expectation wrong | Discuss, update documentation, adjust test |
+
+Failures are treated as **bugs to fix**, not tests to adjust.
+
+## Success Criteria
+
+1. Every public function has documented expectations in source
+2. Tests verify expectations, not current implementation
+3. Property invariants hold for all inputs
+4. No "tests written to pass" - tests define correct behavior independently
+5. All tests pass after fixing surfaced bugs
+
+## Files to Test
+
+### Planning (11 files)
+- TripPlanningEngine.swift
+- GameDAGRouter.swift
+- ItineraryBuilder.swift
+- RouteFilters.swift
+- TravelEstimator.swift
+- ScenarioPlanner.swift
+- ScenarioAPlanner.swift
+- ScenarioBPlanner.swift
+- ScenarioCPlanner.swift
+- ScenarioDPlanner.swift
+- PlanningModels.swift
+
+### Domain (15 files)
+- Game.swift, Stadium.swift, Team.swift, Trip.swift
+- TripStop.swift, TravelSegment.swift, TripPreferences.swift
+- Sport.swift, Region.swift, Division.swift
+- Progress.swift, DynamicSport.swift, TripPoll.swift
+- AnySport.swift, AchievementDefinitions.swift
+
+### Services (23 files)
+- CloudKitService.swift, DataProvider.swift, BootstrapService.swift
+- CanonicalSyncService.swift, BackgroundSyncManager.swift
+- LocationService.swift, LocationPermissionManager.swift
+- AchievementEngine.swift, EVChargingService.swift
+- GameMatcher.swift, StadiumProximityMatcher.swift
+- FreeScoreAPI.swift, HistoricalGameScraper.swift
+- NetworkMonitor.swift, RateLimiter.swift
+- PollService.swift, DeepLinkHandler.swift
+- RouteDescriptionGenerator.swift, SuggestedTripsGenerator.swift
+- SyncCancellationToken.swift, VisitPhotoService.swift
+- PhotoMetadataExtractor.swift, StadiumIdentityService.swift
+
+### Export (2 files)
+- ShareableContent.swift
+- POISearchService.swift
+
+**Total: ~52 source files, estimated 8-10 hours**