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

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

Workflow

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

For MCP Tools

python

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

python

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_<operation>_<scenario>

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