Novault-backend/internal/service/REFUND_SERVICE_TEST_SUMMARY.md

Refund Service Test Summary

Overview

This document summarizes the test coverage for the Refund Service implementation.

Test Files

• refund_service_test.go - Unit tests for refund service

Test Coverage

TestRefundService_ProcessRefund

Tests the main refund processing functionality with various scenarios:

1. Successful Full Refund

   • Creates an expense transaction
   • Processes a full refund (refund amount = original amount)
   • Verifies refund income record is created correctly
   • Verifies original transaction status is updated to "full"
   • Verifies account balance is updated correctly
   • Validates: Requirements 8.13, 8.14, 8.16, 8.28

2. Successful Partial Refund

   • Creates an expense transaction
   • Processes a partial refund (refund amount < original amount)
   • Verifies refund income record is created with correct amount
   • Verifies original transaction status is updated to "partial"
   • Validates: Requirements 8.13, 8.15

3. Transaction Not Found

   • Attempts to refund a non-existent transaction
   • Verifies ErrTransactionNotFound is returned
   • Validates: Error handling

4. Not Expense Transaction

   • Attempts to refund an income transaction
   • Verifies ErrNotExpenseTransaction is returned
   • Validates: Requirement 8.10 (only expense transactions can be refunded)

5. Already Refunded

   • Attempts to refund a transaction that's already refunded
   • Verifies ErrAlreadyRefunded is returned
   • Validates: Requirement 8.17 (duplicate refund protection)

6. Invalid Refund Amount - Zero

   • Attempts to refund with amount = 0
   • Verifies ErrInvalidRefundAmount is returned
   • Validates: Requirement 8.12 (amount validation)

7. Invalid Refund Amount - Negative

   • Attempts to refund with negative amount
   • Verifies ErrInvalidRefundAmount is returned
   • Validates: Requirement 8.12 (amount validation)

8. Invalid Refund Amount - Exceeds Original

   • Attempts to refund with amount > original amount
   • Verifies ErrInvalidRefundAmount is returned
   • Validates: Requirement 8.12 (amount validation)

9. Refund Category Not Found

   • Attempts to refund when system category is missing
   • Verifies ErrRefundCategoryNotFound is returned
   • Validates: Error handling for missing system data

TestRefundService_TransactionAtomicity

Tests that refund operations are atomic:

1. Transaction Atomicity
   • Processes a refund
   • Verifies all changes are committed together:
     • Original transaction status updated
     • Refund income record created
     • Account balance updated
   • Validates: Database transaction atomicity

Key Features Tested

Refund Processing

• ✅ Full refund (amount = original)
• ✅ Partial refund (amount < original)
• ✅ Automatic refund income creation
• ✅ Original transaction status update
• ✅ Account balance update
• ✅ Ledger association (same ledger as original)

Validation

• ✅ Transaction must exist
• ✅ Transaction must be expense type
• ✅ Transaction must not be already refunded
• ✅ Refund amount must be > 0
• ✅ Refund amount must not exceed original amount
• ✅ Refund system category must exist

Data Consistency

• ✅ Database transaction atomicity
• ✅ All related records updated together
• ✅ Account balance correctly adjusted
• ✅ Refund income linked to original transaction

Requirements Validation

Requirement	Test Coverage	Status
8.10 - Only expense transactions can be refunded	TestRefundService_ProcessRefund/not_expense_transaction	✅
8.11 - Display refund amount input dialog	N/A (Frontend)	-
8.12 - Validate refund amount	Multiple test cases	✅
8.13 - Create refund income record	successful_full_refund, successful_partial_refund	✅
8.14 - Mark transaction as refunded	successful_full_refund	✅
8.15 - Display partial refund status	successful_partial_refund	✅
8.16 - Display full refund status	successful_full_refund	✅
8.17 - Prevent duplicate refunds	already_refunded	✅
8.18 - Restore status when deleting refund income	N/A (Not implemented in this task)	-
8.28 - Same ledger as original transaction	successful_full_refund	✅

Test Execution Notes

CGO Requirement

The service tests require CGO to be enabled for SQLite support. To run these tests:

# On systems with GCC installed
CGO_ENABLED=1 go test -v ./internal/service/refund_service_test.go

# Or use Docker for consistent test environment
docker run --rm -v $(pwd):/app -w /app golang:1.21 go test -v ./internal/service/

Alternative Testing

If CGO is not available, the handler tests provide comprehensive coverage of the API layer:

go test -v ./internal/handler/refund_handler_test.go

Integration with Existing Code

The refund service follows the same patterns as the reimbursement service:

• Uses database transactions for atomicity
• Implements proper error handling
• Updates account balances
• Creates linked income records
• Validates business rules

Next Steps

1. Run integration tests in a CGO-enabled environment
2. Test with real PostgreSQL database
3. Add property-based tests (Task 5.4)
4. Implement frontend components for refund UI