Add Comprehensive Test Coverage for Phase 1 Services

[devin-ai-integration]

Add Comprehensive Test Coverage for Banking Microservices (All Phases)

Summary

This PR implements comprehensive test coverage for all 7 microservices in the Banking Microservices application, replacing trivial contextLoads() tests with meaningful unit and integration tests.

Test Coverage Added:

• Phase 1 (Fund Transfer, Transaction, Account): 43 tests
• Phase 2 (User Service, API Gateway): 19 tests
• Phase 3 (Sequence Generator, Service Registry): 9 tests
• Total: 71+ tests across all microservices

Testing Infrastructure:

• H2 in-memory database (jdbc:h2:mem:testdb) for all repository integration tests
• application-test.yml test configurations for all services
• @ActiveProfiles("test") on all test classes
• Mockito for mocking external dependencies (Feign clients, Keycloak)
• @DataJpaTest for repository integration tests
• @ExtendWith(MockitoExtension.class) for service unit tests

Key Testing Patterns:

• Unit tests mock all external dependencies (Keycloak, Feign clients)
• Integration tests verify database persistence with H2
• Exception scenarios covered (ResourceNotFound, InsufficientBalance, ResourceConflict, etc.)
• Service-to-service communication mocked via Feign clients

Notable Implementation Details:

• H2 configured with globally_quoted_identifiers: true to handle reserved SQL keywords (e.g., "user" table)
• Sequence Generator concurrency test uses @TestMethodOrder to control test execution order due to H2 auto-increment behavior
• API Gateway tests disable Eureka and OAuth2 for isolated testing
• User Service tests comprehensively mock Keycloak integration (5 methods)

Review & Testing Checklist for Human

⚠️ Risk Level: Medium-High - Extensive mocking of external dependencies; no CI verification

• Run all tests locally: Execute mvn test for each service (Fund-Transfer, Transaction-Service, Account-Service, User-Service, API-Gateway, Sequence-Generator, Service-Registry) to verify they pass in your environment
• Review Sequence Generator concurrency test results: The SequenceServiceConcurrencyTest.concurrentCreate_demonstratesThreadSafetyIssue() test demonstrates potential race conditions under concurrent load. Review the console output to understand the thread-safety behavior. This is documented behavior, not a bug in this PR, but may need separate attention.
• Verify mocked behavior accuracy: Review the mocked Keycloak integration in UserServiceImplTest to ensure it accurately represents real Keycloak behavior, especially for user creation (expecting 201 status) and status updates (enabling/disabling accounts)
• Consider H2 vs MySQL differences: Tests use H2 in-memory database while production uses MySQL. Verify that H2 schema generation matches production schema, especially for the "user" table with reserved keyword handling
• OAuth2/JWT security gap: API Gateway tests disable OAuth2 for testing. Consider if separate security integration tests are needed for Keycloak/JWT token validation

Test Plan

# Run all tests for each service
cd ~/repos/BankingMicroservices
for service in Fund-Transfer Transaction-Service Account-Service User-Service API-Gateway Sequence-Generator Service-Registry; do 
  echo "Testing $service..."; 
  cd $service && mvn test -q && cd ..; 
done

Notes

• All tests verified locally (no CI configured for this repository)
• Keycloak integration is fully mocked in User Service tests
• Feign client inter-service communication is mocked in all service tests
• Concurrency test for Sequence Generator demonstrates existing thread-safety issues but does not fix them (as requested in task scope)

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Link to Devin run: https://app.devin.ai/sessions/b29d1565cf644123a9b6185ccfde593e
Requested by: Sam Fertig (@samfert-codeium)

[devin-ai-integration]

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