feat: add backend tests for AI chat builder + fix conversation_id FK issue

Tests cover session create, send message with tree update, get session,
abandon, 404 on missing session, and 503 when AI disabled.

Fixed: ai_usage.conversation_id has FK to ai_conversations, not
ai_chat_sessions. Chat builder now passes conversation_id=None and
tracks session reference in extra_data.chat_session_id.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

backend/app/api/endpoints/ai_chat.py

@@ -106,7 +106,7 @@ async def create_session(
     await record_ai_usage(
         user_id=current_user.id,
         account_id=current_user.account_id,
-        conversation_id=session.id,
+        conversation_id=None,
         generation_type="chat_message",
         tier=plan,
         input_tokens=session.total_input_tokens,
@@ -118,7 +118,7 @@ async def create_session(
         succeeded=True,
         counts_toward_quota=False,
         error_code=None,
-        extra_data={"phase": "scoping"},
+        extra_data={"phase": "scoping", "chat_session_id": str(session.id)},
         db=db,
     )
 
@@ -175,7 +175,7 @@ async def post_message(
         await record_ai_usage(
             user_id=current_user.id,
             account_id=current_user.account_id,
-            conversation_id=session.id,
+            conversation_id=None,
             generation_type="chat_message",
             tier=plan,
             input_tokens=0,
@@ -184,7 +184,7 @@ async def post_message(
             succeeded=False,
             counts_toward_quota=False,
             error_code=type(e).__name__,
-            extra_data=None,
+            extra_data={"chat_session_id": str(session.id)},
             db=db,
         )
         await db.commit()
@@ -198,7 +198,7 @@ async def post_message(
     await record_ai_usage(
         user_id=current_user.id,
         account_id=current_user.account_id,
-        conversation_id=session.id,
+        conversation_id=None,
         generation_type="chat_message",
         tier=plan,
         input_tokens=input_delta,
@@ -210,7 +210,7 @@ async def post_message(
         succeeded=True,
         counts_toward_quota=False,
         error_code=None,
-        extra_data={"phase": session.current_phase},
+        extra_data={"phase": session.current_phase, "chat_session_id": str(session.id)},
         db=db,
     )
 
@@ -288,7 +288,7 @@ async def generate_tree(
         await record_ai_usage(
             user_id=current_user.id,
             account_id=current_user.account_id,
-            conversation_id=session.id,
+            conversation_id=None,
             generation_type="chat_generate",
             tier=plan,
             input_tokens=session.total_input_tokens - prev_input,
@@ -297,7 +297,7 @@ async def generate_tree(
             succeeded=False,
             counts_toward_quota=False,
             error_code="invalid_output",
-            extra_data={"error": str(e)},
+            extra_data={"error": str(e), "chat_session_id": str(session.id)},
             db=db,
         )
         await db.commit()
@@ -312,7 +312,7 @@ async def generate_tree(
         await record_ai_usage(
             user_id=current_user.id,
             account_id=current_user.account_id,
-            conversation_id=session.id,
+            conversation_id=None,
             generation_type="chat_generate",
             tier=plan,
             input_tokens=input_delta,
@@ -321,7 +321,7 @@ async def generate_tree(
             succeeded=False,
             counts_toward_quota=False,
             error_code=type(e).__name__,
-            extra_data={"error": str(e)},
+            extra_data={"error": str(e), "chat_session_id": str(session.id)},
             db=db,
         )
         await db.commit()
@@ -342,7 +342,7 @@ async def generate_tree(
     await record_ai_usage(
         user_id=current_user.id,
         account_id=current_user.account_id,
-        conversation_id=session.id,
+        conversation_id=None,
         generation_type="chat_generate",
         tier=plan,
         input_tokens=input_delta,
@@ -354,7 +354,7 @@ async def generate_tree(
         succeeded=True,
         counts_toward_quota=True,
         error_code=None,
-        extra_data=None,
+        extra_data={"chat_session_id": str(session.id)},
         db=db,
     )
 

backend/tests/test_ai_chat.py

@@ -0,0 +1,187 @@
+"""Integration tests for AI Chat Builder endpoints.
+
+These tests mock the AI provider to avoid real API calls.
+"""
+import pytest
+from unittest.mock import AsyncMock, patch
+
+pytestmark = pytest.mark.asyncio
+
+
+@pytest.fixture
+def mock_ai_provider():
+    """Mock AI provider that returns realistic responses."""
+    provider = AsyncMock()
+    provider.generate_text = AsyncMock(return_value=(
+        "Great question! Let's build a troubleshooting flow for DNS resolution issues. "
+        "To start, I need to understand the scope.\n\n"
+        "Who is the target audience for this flow? Are we targeting:\n"
+        "- Tier 1 help desk (basic checks only)\n"
+        "- Tier 2 desktop support (intermediate diagnostics)\n"
+        "- Tier 3 systems engineers (deep DNS troubleshooting)\n\n"
+        "[PHASE:scoping]",
+        500,  # input tokens
+        200,  # output tokens
+    ))
+    return provider
+
+
+async def test_create_chat_session(client, auth_headers, mock_ai_provider):
+    """POST /ai/chat/sessions creates a session and returns AI greeting."""
+    with patch("app.core.ai_chat_service.get_ai_provider", return_value=mock_ai_provider):
+        resp = await client.post(
+            "/api/v1/ai/chat/sessions",
+            json={"flow_type": "troubleshooting"},
+            headers=auth_headers,
+        )
+
+    assert resp.status_code == 201
+    data = resp.json()
+    assert "session_id" in data
+    assert "greeting" in data
+    assert data["current_phase"] == "scoping"
+    assert len(data["greeting"]) > 0
+
+
+async def test_send_message(client, auth_headers, mock_ai_provider):
+    """POST /ai/chat/sessions/{id}/messages returns AI response."""
+    # Create session first
+    with patch("app.core.ai_chat_service.get_ai_provider", return_value=mock_ai_provider):
+        create_resp = await client.post(
+            "/api/v1/ai/chat/sessions",
+            json={"flow_type": "troubleshooting"},
+            headers=auth_headers,
+        )
+    session_id = create_resp.json()["session_id"]
+
+    # Mock response with tree update — must pass validate_generated_tree (min 5 nodes)
+    import json
+    tree_obj = {
+        "id": "root", "type": "decision",
+        "question": "What DNS symptom is the user experiencing?",
+        "options": [
+            {"id": "opt-1", "label": "Cannot resolve any domains", "next_node_id": "dns-check"},
+            {"id": "opt-2", "label": "Intermittent failures", "next_node_id": "dns-cache-fix"},
+        ],
+        "children": [
+            {
+                "id": "dns-check", "type": "decision",
+                "question": "Is the DNS Client service running?",
+                "options": [
+                    {"id": "dc-1", "label": "Yes", "next_node_id": "dns-fwd-fix"},
+                    {"id": "dc-2", "label": "No", "next_node_id": "dns-svc-fix"},
+                ],
+                "children": [
+                    {"id": "dns-fwd-fix", "type": "solution", "title": "Check DNS Forwarders",
+                     "description": "DNS forwarders may be misconfigured",
+                     "resolution_steps": ["Check forwarder config"]},
+                    {"id": "dns-svc-fix", "type": "solution", "title": "Restart DNS Service",
+                     "description": "DNS Client service is stopped",
+                     "resolution_steps": ["Start-Service Dnscache"]},
+                ],
+            },
+            {"id": "dns-cache-fix", "type": "solution", "title": "Stale DNS Cache",
+             "description": "DNS cache has stale entries",
+             "resolution_steps": ["ipconfig /flushdns"]},
+        ],
+    }
+    tree_json = json.dumps(tree_obj)
+    mock_ai_provider.generate_text = AsyncMock(return_value=(
+        "Good, targeting Tier 2 support. Let's start with the first diagnostic question.\n\n"
+        "The root question should be: 'What DNS symptom is the user experiencing?'\n\n"
+        f"[TREE_UPDATE]\n{tree_json}\n[/TREE_UPDATE]\n\n"
+        "[PHASE:discovery]",
+        800,
+        400,
+    ))
+
+    with patch("app.core.ai_chat_service.get_ai_provider", return_value=mock_ai_provider):
+        resp = await client.post(
+            f"/api/v1/ai/chat/sessions/{session_id}/messages",
+            json={"content": "This is for Tier 2 support, hybrid environment with on-prem AD."},
+            headers=auth_headers,
+        )
+
+    assert resp.status_code == 200
+    data = resp.json()
+    assert "content" in data
+    assert data["current_phase"] == "discovery"
+    assert data["working_tree"] is not None
+    assert data["working_tree"]["type"] == "decision"
+    # Markers should be stripped from content
+    assert "[TREE_UPDATE]" not in data["content"]
+    assert "[PHASE:" not in data["content"]
+
+
+async def test_get_session(client, auth_headers, mock_ai_provider):
+    """GET /ai/chat/sessions/{id} returns full session state."""
+    with patch("app.core.ai_chat_service.get_ai_provider", return_value=mock_ai_provider):
+        create_resp = await client.post(
+            "/api/v1/ai/chat/sessions",
+            json={"flow_type": "troubleshooting"},
+            headers=auth_headers,
+        )
+    session_id = create_resp.json()["session_id"]
+
+    resp = await client.get(
+        f"/api/v1/ai/chat/sessions/{session_id}",
+        headers=auth_headers,
+    )
+
+    assert resp.status_code == 200
+    data = resp.json()
+    assert data["session_id"] == session_id
+    assert data["status"] == "active"
+    assert data["flow_type"] == "troubleshooting"
+    # Hidden primer message should be filtered out
+    assert all(
+        msg.get("role") == "assistant" or not msg.get("hidden")
+        for msg in data["conversation_history"]
+    )
+
+
+async def test_abandon_session(client, auth_headers, mock_ai_provider):
+    """DELETE /ai/chat/sessions/{id} sets status to abandoned."""
+    with patch("app.core.ai_chat_service.get_ai_provider", return_value=mock_ai_provider):
+        create_resp = await client.post(
+            "/api/v1/ai/chat/sessions",
+            json={"flow_type": "troubleshooting"},
+            headers=auth_headers,
+        )
+    session_id = create_resp.json()["session_id"]
+
+    resp = await client.delete(
+        f"/api/v1/ai/chat/sessions/{session_id}",
+        headers=auth_headers,
+    )
+    assert resp.status_code == 204
+
+    # Verify session is abandoned
+    get_resp = await client.get(
+        f"/api/v1/ai/chat/sessions/{session_id}",
+        headers=auth_headers,
+    )
+    assert get_resp.json()["status"] == "abandoned"
+
+
+async def test_session_not_found(client, auth_headers):
+    """Accessing nonexistent session returns 404."""
+    import uuid
+    fake_id = str(uuid.uuid4())
+    resp = await client.get(
+        f"/api/v1/ai/chat/sessions/{fake_id}",
+        headers=auth_headers,
+    )
+    assert resp.status_code == 404
+
+
+async def test_ai_disabled_returns_503(client, auth_headers):
+    """When AI is not configured, endpoints return 503."""
+    with patch("app.api.endpoints.ai_chat.settings") as mock_settings:
+        mock_settings.ai_enabled = False
+        resp = await client.post(
+            "/api/v1/ai/chat/sessions",
+            json={"flow_type": "troubleshooting"},
+            headers=auth_headers,
+        )
+    assert resp.status_code == 503