Added Jest configuration and unit tests:
- jest.config.js: Jest configuration with ts-jest
- setup.ts: Global test setup with custom matchers
Test files (30 tests passing):
- service-order.service.test.ts: CRUD, status transitions, cost calculation
- diagnostic.service.test.ts: CRUD, OBD codes, completion workflow
- part.service.test.ts: CRUD, stock management, low stock alerts
- vehicle.service.test.ts: CRUD, VIN validation, odometer updates
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
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