feat: Add comprehensive test coverage for calendar cache and sync functionality

[volnei]

What does this PR do?

This PR adds comprehensive test coverage for the calendar cache and sync functionality implemented in PR #23876. It provides extensive test suites for all major components of the calendar caching system including:

• CalendarCacheRepository - Tests for cache retrieval, storage, watching/unwatching calendars
• CalendarCacheEventService & Repository - Tests for event handling, filtering, and batch operations
• API v2 CalendarsCacheService - Tests for Redis-based caching operations with TTL
• Cron job functionality - Tests for automated cache cleanup and calendar synchronization
• Provider-specific implementations - Tests for Google Calendar and Office365 webhook integrations
• Utility functions - Tests for cache serving logic and feature flag handling

The test suite follows Cal.com's established patterns using Vitest and Prismock, ensuring consistent timezone handling with TZ=UTC.

Link to Devin run: https://app.devin.ai/sessions/d4c8af423e9a47efa4d61a60b2577653
Requested by: @volnei

Visual Demo (For contributors especially)

N/A - This PR focuses on test coverage and does not introduce user-facing changes.

Mandatory Tasks (DO NOT REMOVE)

• I have self-reviewed the code (A decent size PR without self-review might be rejected).
• I have updated the developer docs in /docs if this PR makes changes that would require a documentation change. If N/A, write N/A here and check the checkbox.
• I confirm automated tests are in place that prove my fix is effective or that my feature works.

How should this be tested?

Environment Setup

• No additional environment variables required for tests
• Tests use mocked dependencies (Redis, Prisma, calendar providers)

Running Tests

# Run all calendar cache tests
TZ=UTC yarn test packages/features/calendar-cache
TZ=UTC yarn test packages/features/calendar-subscription/lib/cache
TZ=UTC yarn test apps/api/v2/src/ee/calendars/services
TZ=UTC yarn test apps/web/app/api/cron/calendar-cache-cleanup

# Run enhanced CalendarService tests
TZ=UTC yarn test packages/app-store/googlecalendar/lib/__tests__/CalendarService.test.ts

# Run type checking
yarn type-check:ci --force

# Run linting
yarn lint:report

Test Coverage Areas

• Cache Operations: Hit/miss scenarios, TTL behavior, Redis operations
• Event Processing: Filtering, batch operations, status handling
• Delegation Credentials: In-memory vs database credential scenarios
• Cron Jobs: Calendar watching/unwatching, cleanup operations
• Error Handling: Database errors, network failures, invalid data
• Feature Flags: Enabled/disabled behavior across components

Expected Results

• All 124+ tests should pass consistently
• Type checking should complete without errors
• Linting should pass with no warnings
• Tests should complete in reasonable time (<30 seconds total)

Checklist

• I haven't read the contributing guide
• My code doesn't follow the style guidelines of this project
• I haven't commented my code, particularly in hard-to-understand areas
• I haven't checked if my changes generate no new warnings

Key Areas for Review

⚠️ Important Review Points:

1. Test Coverage Completeness - Verify tests cover all critical paths in the calendar cache implementation
2. Mock Accuracy - Ensure mocks properly simulate real service behavior without hiding bugs
3. Error Scenarios - Review error handling tests for realistic failure modes
4. Integration Points - Check tests properly validate interactions between cache layers
5. Performance Considerations - Verify tests don't introduce performance regressions
6. Type Safety - Confirm all type assertions are safe and necessary

Files Added/Modified

New Test Files (13 files)

• packages/features/calendar-cache/calendar-cache.repository.test.ts
• packages/features/calendar-cache/calendar-cache.test.ts
• packages/features/calendar-cache/api/cron.test.ts
• packages/features/calendar-cache/lib/getShouldServeCache.test.ts
• packages/features/calendar-subscription/lib/cache/CalendarCacheEventService.test.ts
• packages/features/calendar-subscription/lib/cache/CalendarCacheEventRepository.test.ts
• apps/api/v2/src/ee/calendars/services/calendars-cache.service.test.ts
• apps/web/app/api/cron/calendar-cache-cleanup/route.test.ts
• packages/app-store/googlecalendar/lib/__tests__/webhook-cache-integration.test.ts
• packages/app-store/office365calendar/lib/__tests__/webhook-cache-integration.test.ts

Mock Infrastructure (3 files)

• packages/features/calendar-cache/__mocks__/CalendarCacheEventRepository.mock.ts
• packages/features/calendar-cache/__mocks__/CalendarProvider.mock.ts
• packages/features/calendar-cache/__mocks__/RedisService.mock.ts

Enhanced Existing Tests (1 file)

• packages/app-store/googlecalendar/lib/__tests__/CalendarService.test.ts - Re-enabled cache tests, added delegation credential scenarios

This comprehensive test suite ensures the calendar cache system is reliable, maintainable, and follows Cal.com's quality standards.

[devin-ai-integration]

🤖 Devin AI Engineer

I'll be helping with this pull request! Here's what you should know:

✅ I will automatically:

• Address comments on this PR that start with 'DevinAI'.
• Look at CI failures and help fix them

Note: I can only respond to comments from users who have write access to this repository.

⚙️ Control Options:

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✨ Finishing touches

🧪 Generate unit tests

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch feat/calendar_sync_cache_tests

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2 Skipped Deployments

Project	Deployment	Preview	Comments	Updated (UTC)
cal	Ignored			Sep 18, 2025 9:50pm
cal-eu	Ignored			Sep 18, 2025 9:50pm