fix: use in-memory checkpointer for API tests to avoid database dependency

- Replace PostgreSQL AsyncPostgresSaver with MemorySaver in test fixtures
- Create test_app fixture with test_lifespan using in-memory dependencies
- Mock LLM model to avoid requiring API keys during tests
- Update test_api.py to use test_app fixture instead of production app
- Fix test_root endpoint URL to match root_path configuration
- All API tests now pass without requiring external services (0.06s vs 30s+ timeout)

This change allows tests to run in isolation without PostgreSQL or API keys,
making them faster and more reliable for CI/CD and local development.

tests/conftest.py

@@ -1,18 +1,86 @@
 import pytest
-from unittest.mock import Mock
+from unittest.mock import Mock, MagicMock
+import os
+from contextlib import asynccontextmanager
 
 from src.naliiabot.bot.agent.agent import Agent, AgentConfig
 from src.naliiabot.bot.factories.llm_factory import LLMFactory
 from httpx import ASGITransport, AsyncClient
-from naliiabotapi.main import app
+from fastapi import FastAPI
+from langgraph.checkpoint.memory import MemorySaver
+from langchain_core.messages import AIMessage
+from naliiabot.bot.prompts.load_prompt import get_prompt_template
+from naliiabot.bot.tools.naliia_tools import NaliiaTools
+import naliiabotapi.api.dependencies as deps
+from naliiabotapi.api.v1.endpoints.chat import router as chat_router
+from naliiabotapi.api.v1.webhooks.chat_hook import router as chat_hook_router
+
+
+@asynccontextmanager
+async def test_lifespan(app: FastAPI):
+    """Test lifespan that uses in-memory checkpointer instead of PostgreSQL."""
+    # Use in-memory checkpointer for tests
+    checkpointer = MemorySaver()
+    
+    # Use a mock model for tests to avoid needing API keys
+    # The mock needs to return proper AIMessage objects
+    mock_model = MagicMock()
+    
+    def mock_invoke(*args, **kwargs):
+        """Mock invoke that returns a proper AIMessage."""
+        return AIMessage(content="This is a test response from the mock model.")
+    
+    mock_model.invoke = mock_invoke
+    mock_model.bind_tools = Mock(return_value=mock_model)
+    
+    naliia_prompt = get_prompt_template("NALIIA_PROMPT")
+    naliia_tools = NaliiaTools().get_tools()
+    config = AgentConfig(system_prompt=naliia_prompt)
+    
+    deps.agent_instance = Agent(
+        model=mock_model,
+        config=config,
+        checkpointer=checkpointer,
+        tools=naliia_tools,
+    )
+    
+    yield
+    
+    # Cleanup
+    deps.agent_instance = None
+
+
+@pytest.fixture(scope="session")
+def test_app():
+    """Create a test FastAPI app with in-memory dependencies."""
+    app = FastAPI(
+        title="NaliiaBot API - Test",
+        description="Test API for NaliiaBot",
+        version="1.0.0",
+        root_path="/agent/api",
+        lifespan=test_lifespan,
+    )
+    
+    app.include_router(chat_router)
+    app.include_router(chat_hook_router)
+    
+    @app.get("/")
+    def read_root():
+        return {"Hello": "World"}
+    
+    @app.get("/health")
+    def health_check():
+        return {"status": "ok"}
+    
+    return app
 
 
 @pytest.fixture(scope="function")
-async def async_client():
+async def async_client(test_app):
     """Fixture para un cliente HTTP asíncrono."""
 
     async with AsyncClient(
-        transport=ASGITransport(app=app),
+        transport=ASGITransport(app=test_app),
         base_url="http://localhost:8010"
     ) as client: