Empty package marker.

Shared pytest fixtures:

• mock_rag_system — MagicMock pre-wired with query(), get_course_analytics(), and session_manager.create_session() return values
• test_app — inline FastAPI app that mirrors the routes from app.py without static file mounting or ChromaDB initialisation; closes over mock_rag_system so per-test mutations are reflected
• client — TestClient wrapping test_app

13 API endpoint tests across two classes:

TestQueryEndpoint

• test_returns_answer_and_sources — happy path response shape
• test_uses_provided_session_id — session_id passed through to RAG and returned
• test_creates_session_when_none_provided — session created automatically when omitted
• test_returns_empty_sources_list — empty sources list handled correctly
• test_missing_required_query_field_returns_422 — validation error on missing query
• test_empty_body_returns_422 — validation error on empty body
• test_rag_error_returns_500 — RAG exception surfaces as 500 with detail message
• test_response_has_all_required_fields — all three fields present in response

TestCoursesEndpoint

• test_returns_course_list — correct count and titles
• test_total_courses_matches_titles_length — count is consistent with list length
• test_response_has_all_required_fields — both fields present
• test_empty_course_list — zero courses handled correctly
• test_rag_error_returns_500 — RAG exception surfaces as 500 with detail message

Added pytest configuration and dev dependencies:

[dependency-groups]
dev = [
    "pytest>=8.0",
    "httpx>=0.27",
]

[tool.pytest.ini_options]
testpaths = ["backend/tests"]
pythonpath = ["backend"]

app.py initialises RAGSystem at module level and mounts StaticFiles from ../frontend, both of which fail in a test environment (no ChromaDB, no frontend build). The test app in conftest.py defines the same endpoint logic inline with a mocked RAGSystem, avoiding the import entirely. Tests that need to change mock behaviour (error cases) receive both client and mock_rag_system as fixtures — pytest gives them the same object instance within a test, so side_effect mutations work correctly.