test-gen

name	test-gen
description	Generate comprehensive pytest integration tests for MCP tools and FastAPI endpoints. Includes fixtures, edge cases, and validation tests.

Pytest Test Generator

Purpose

Auto-generate integration tests following project's pytest patterns with proper fixtures, database sessions, and >80% coverage for business logic.

Core Rules

1. Context7 First: Query /websites/sqlmodel_tiangolo for testing patterns
2. Use Project Fixtures: Leverage conftest.py fixtures (session, sample_todo, sample_todos)
3. Test-Driven: Generate tests BEFORE or ALONGSIDE implementation
4. Coverage Target: >80% for business logic
5. Integration Focus: Test database persistence, not mocks

Workflow

1. Identify Target: MCP tool or FastAPI endpoint to test
2. Read conftest.py: Understand available fixtures
3. Query Context7: Fetch SQLModel + FastAPI testing patterns
4. Generate Test Suite:

For MCP Tools

import pytest
from sqlmodel import select
from src.mcp_server.models import Todo, TodoStatus
from src.mcp_server.tools.operation_name import operation_name

def test_operation_success(session):
    """Test successful operation with valid input."""
    result = operation_name(
        param="value",
        _test_session=session
    )

    import json
    data = json.loads(result)

    assert data["success"] is True
    assert "data" in data

    # Verify database persistence
    statement = select(Todo).where(Todo.id == data["data"]["id"])
    todo = session.exec(statement).first()

    assert todo is not None
    assert todo.title == "Expected Value"


def test_operation_not_found(session):
    """Test operation with non-existent resource."""
    result = operation_name(
        param="nonexistent",
        _test_session=session
    )

    import json
    data = json.loads(result)

    assert data["success"] is False
    assert "error" in data


def test_operation_validation_error(session):
    """Test operation with invalid input."""
    result = operation_name(
        param="",  # Invalid empty string
        _test_session=session
    )

    import json
    data = json.loads(result)

    assert data["success"] is False


def test_operation_with_optional_params(session):
    """Test operation with all optional parameters."""
    result = operation_name(
        required_param="value",
        optional_param="extra",
        _test_session=session
    )

    import json
    data = json.loads(result)

    assert data["success"] is True

For FastAPI Endpoints

from fastapi.testclient import TestClient
from src.main import app

client = TestClient(app)

def test_create_endpoint(session):
    """Test POST endpoint with valid data."""
    response = client.post(
        "/todos/",
        json={"title": "Test Todo", "description": "Test"}
    )

    assert response.status_code == 200
    data = response.json()

    assert data["title"] == "Test Todo"
    assert data["id"] is not None

    # Verify database
    from src.mcp_server.models import Todo
    from sqlmodel import select
    todo = session.exec(select(Todo).where(Todo.id == data["id"])).first()
    assert todo is not None


def test_create_endpoint_validation_error(session):
    """Test POST endpoint with missing required field."""
    response = client.post("/todos/", json={"description": "No title"})

    assert response.status_code == 422  # Validation error


def test_get_endpoint_not_found(session):
    """Test GET endpoint with non-existent ID."""
    response = client.get("/todos/99999")

    assert response.status_code == 404
    assert "not found" in response.json()["detail"].lower()

Test Categories

Happy Path Tests

• Valid input with all required fields
• Valid input with optional fields
• Successful database persistence

Edge Cases

• Empty strings
• Maximum length values
• Boundary values (offset=0, limit=100)
• Special characters

Error Cases

• Missing required fields (422)
• Resource not found (404)
• Invalid enum values
• Duplicate constraints

Integration Tests

• Verify database state after operations
• Test cascading operations
• Check related entity updates

Output Format

• Complete test file with imports
• Descriptive test names and docstrings
• Multiple test functions covering scenarios
• Proper assertions (success, data, database state)
• Uses project fixtures (session, sample_todo)

Quality Checks

• ✓ Each test has clear docstring
• ✓ Uses _test_session for MCP tools
• ✓ Verifies database persistence
• ✓ Tests both success and failure paths
• ✓ Assertions check JSON structure
• ✓ Follows naming: test__

Example Usage

User: "Generate tests for update_todo tool" Action: Read update_todo.py → Query Context7 → Generate test_update_todo.py with 5-7 test cases → Verify fixture usage