Add comprehensive unit tests for critical controllers and services

[devin-ai-integration]

Add Comprehensive Unit Tests for Critical Controllers and Services

Summary

This PR adds 62 comprehensive unit tests across the three core microservices in the BankingMicroservices project, focusing on the most critical business logic:

Test Files Added:

• Fund-Transfer Service: 15 tests (10 service + 5 controller)

  • FundTransferServiceImplTest.java - Tests fund transfer validation, account verification, balance checks
  • FundTransferControllerTest.java - Tests all 3 REST endpoints

• Account-Service: 30 tests (21 service + 9 controller)

  • AccountServiceImplTest.java - Tests account creation, status updates, closure, balance validation
  • AccountControllerTest.java - Tests all 8 REST endpoints

• Transaction-Service: 17 tests (11 service + 6 controller)

  • TransactionServiceTest.java - Tests deposits, withdrawals, internal transfers
  • TransactionControllerTest.java - Tests all 4 REST endpoints

Coverage Includes:

✅ All validation paths (account status, balance checks, user existence)
✅ Edge cases (insufficient balance, boundary conditions, null responses)
✅ Exception handling (ResourceNotFound, AccountStatusException, InsufficientBalance)
✅ Mocked external dependencies (Feign clients, repositories)
✅ All controller endpoints with various HTTP status codes

All 62 tests pass successfully ✅

Review & Testing Checklist for Human

⚠️ Important: These are unit tests with mocked dependencies. Real integration behavior needs verification.

• Critical Business Logic: Verify the balance validation logic - code requires balance > amount (not >=), meaning transferring your exact balance will fail. Confirm this is intended behavior.

• Minimum Balance Rule: Test account activation with exactly Rs.1000 balance (should succeed) and Rs.999 balance (should fail). The code has a Rs.1000 minimum requirement.

• End-to-End Integration: Test a complete fund transfer flow with all services running:

  1. Create two accounts
  2. Activate both accounts (ensure balance >= Rs.1000)
  3. Perform fund transfer between them
  4. Verify balances updated correctly
  5. Check transaction records are accurate

• Mock Accuracy: Verify that the mocked Feign client responses in tests match actual service behavior, especially:

  • How AccountService returns null for not-found accounts
  • ResponseEntity body patterns
  • Exception types and messages

Notes

• AccountType Enum: Tests use SAVINGS_ACCOUNT constant (not SAVINGS)
• Exception Status Codes: GlobalExceptionHandler returns HTTP 400 for ResourceNotFound exceptions
• Transaction-Service Build: Had to run mvn clean compile to resolve Lombok annotation processing - may indicate build cache sensitivity

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Devin Session: https://app.devin.ai/sessions/39e1bc5155604ffa9f6d1c4659b86458
Requested by: Sam Fertig (@samfert-codeium)

[devin-ai-integration]

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