Add API router tests for unified conversation endpoints

[manavgup]

Problem

PR #589 unified the /api/chat and /api/conversations routers but did not include API router tests for the 8 new endpoints. These endpoints need comprehensive test coverage before the deprecated chat router can be removed.

Endpoints Requiring Tests

The following endpoints in backend/rag_solution/router/conversation_router.py need API tests:

1. POST /{session_id}/messages - Add message to session
2. POST /{session_id}/process - Process user message with LLM (token-consuming)
3. POST /{session_id}/summaries - Create conversation summary
4. GET /{session_id}/summaries - Get conversation summaries
5. POST /{session_id}/context-summarization - Context-aware summarization
6. GET /{session_id}/context-threshold - Check context window threshold
7. POST /{session_id}/conversation-suggestions - Enhanced suggestions
8. POST /{session_id}/enhanced-export - Enhanced export with filters

Test Requirements

For each endpoint, tests should cover:

1. Authentication & Authorization

• Valid authenticated user can access
• Unauthenticated request returns 401
• User cannot access other users' sessions (403)

2. Input Validation

• Valid input succeeds
• Invalid UUID returns 400
• Missing required fields return 422
• Invalid data types return 422

3. Success Cases

• Endpoint returns expected schema
• Data is correctly persisted (where applicable)
• Response includes proper status codes (200, 201)

4. Error Cases

• Session not found returns 404
• Database errors return 500
• Service errors are handled gracefully

5. Business Logic

• LLM integration works (for /process endpoint)
• Summaries are created correctly
• Context threshold calculation is accurate
• Export includes requested data

Implementation Plan

File to Create: tests/api/test_conversation_router.py

Estimated Size: ~300-400 lines (8 endpoints × ~40 lines per endpoint)

Test Structure:

import pytest
from fastapi.testclient import TestClient
from uuid import uuid4

class TestConversationRouterAuth:
    """Test authentication and authorization."""
    
    def test_unauthenticated_request_returns_401(self, client):
        """All endpoints require authentication."""
        # Test each endpoint without auth token
        
    def test_unauthorized_access_returns_403(self, client, test_user):
        """Users cannot access other users' sessions."""
        # Create session for user A, try to access with user B

class TestAddMessage:
    """Test POST /{session_id}/messages endpoint."""
    
    def test_add_message_success(self, client, test_session, auth_headers):
        """Successfully add message to session."""
        
    def test_add_message_invalid_session_returns_404(self, client, auth_headers):
        """Invalid session ID returns 404."""
        
    def test_add_message_missing_content_returns_422(self, client, test_session, auth_headers):
        """Missing message content returns 422."""

class TestProcessMessage:
    """Test POST /{session_id}/process endpoint."""
    
    def test_process_message_success(self, client, test_session, auth_headers, mock_llm):
        """Successfully process message with LLM."""
        
    def test_process_message_consumes_tokens(self, client, test_session, auth_headers, mock_llm):
        """Verify token tracking for LLM calls."""

# ... similar classes for each endpoint

Fixtures Needed:

• client: FastAPI TestClient
• test_user: Test user with UUID
• test_session: Test conversation session
• auth_headers: Authorization headers with JWT token
• mock_llm: Mocked LLM provider for testing
• test_db: Test database session

Acceptance Criteria

• All 8 endpoints have comprehensive test coverage
• Tests cover authentication, validation, success, and error cases
• Tests use proper fixtures and mocks (no real LLM calls)
• All tests pass in CI
• Test coverage for conversation_router.py reaches 80%+
• Tests are documented with clear descriptions

Related

• Depends On: PR feat: Implement Phase 4 Router Unification (Issue #558) #589 (Router Unification)
• Blocks: Removal of deprecated chat_router.py
• Related: Issue Phase 4: Conversation Router Unification #558 (Router Unification)

Priority

HIGH - These tests are required before we can safely remove the deprecated chat router and complete the Phase 4 refactoring.

Estimated Effort

2-3 hours of focused development + testing