Implement comprehensive test coverage for Phase 1 and Phase 2

[devin-ai-integration]

Implement comprehensive test coverage for Phase 1 and Phase 2

Summary

This PR implements comprehensive test coverage improvements for the Spring Boot RealWorld application, focusing on Phase 1 (GraphQL API tests) and Phase 2 (Service layer tests). The implementation includes:

Phase 1 - GraphQL API Tests:

• GraphQLIntegrationTest - General GraphQL queries with authentication setup
• UserMutationTest - GraphQL user operations (registration, login, updates)
• GraphQLErrorHandlingTest - Error scenarios and validation handling

Phase 2 - Service Layer Tests:

• ArticleCommandServiceTest - Article creation and update operations
• UserServiceTest - User registration and update operations
• UpdateUserValidatorTest - Validation logic testing with proper Spring context
• Enhanced ArticleTest - Comprehensive slug generation and update scenarios
• UserTest - User domain entity operations

Production Bug Fix:

• Fixed UpdateUserValidator in UserService.java to properly handle null email/username values during validation

All tests follow existing patterns in the codebase and achieve 129 passing tests with proper lint formatting.

Review & Testing Checklist for Human

🔴 High Priority - Critical Areas to Verify:

• Validate UpdateUserValidator Fix: Test user update functionality manually to ensure the null handling changes don't break existing email/username uniqueness validation
• Verify GraphQL Authentication: Test the GraphQL /graphql endpoint manually with real JWT tokens to ensure authentication works as expected (the tests use mocked authentication)
• Check Parameter Order Fix: Verify that UpdateArticleParam constructor parameter order is (title, body, description) by testing article updates through the REST API
• Test Validation Edge Cases: Manually test user registration/update with duplicate emails, usernames, and null values to ensure validation behaves correctly
• Run Full Test Suite: Execute ./gradlew test to confirm all 129 tests pass in your environment

Notes

• The GraphQL tests use heavy mocking and manual SecurityContext setup, so end-to-end testing of the GraphQL API is recommended
• UpdateUserValidatorTest uses @SpringBootTest instead of DbTestBase to ensure full validation framework is loaded
• Fixed a parameter order bug in ArticleCommandServiceTest where UpdateArticleParam constructor parameters were being passed in wrong order

Requested by: Gardner Johnson (@gardnerjohnson-creator)
Link to Devin run: https://app.devin.ai/sessions/b666a768febd4ae7bd9728cfca01978f

[devin-ai-integration]

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