Backend Testing Guide

This guide covers testing practices for the AutoGPT Platform backend, with a focus on snapshot testing for API endpoints.

Table of Contents

• Overview
• Running Tests
• Snapshot Testing
• Writing Tests for API Routes
• Best Practices

Overview

The backend uses pytest for testing with the following key libraries:

• pytest - Test framework
• pytest-asyncio - Async test support
• pytest-mock - Mocking support
• pytest-snapshot - Snapshot testing for API responses

Running Tests

Run all tests

poetry run test

Run specific test file

poetry run pytest path/to/test_file.py

Run with verbose output

poetry run pytest -v

Run with coverage

poetry run pytest --cov=backend

Snapshot Testing

Snapshot testing captures the output of your code and compares it against previously saved snapshots. This is particularly useful for testing API responses.

How Snapshot Testing Works

1. First run: Creates snapshot files in snapshots/ directories
2. Subsequent runs: Compares output against saved snapshots
3. Changes detected: Test fails if output differs from snapshot

Creating/Updating Snapshots

When you first write a test or when the expected output changes:

poetry run pytest path/to/test.py --snapshot-update

⚠️ Important: Always review snapshot changes before committing! Use git diff to verify the changes are expected.

Snapshot Test Example

import json
from pytest_snapshot.plugin import Snapshot

def test_api_endpoint(snapshot: Snapshot):
    response = client.get("/api/endpoint")
    
    # Snapshot the response
    snapshot.snapshot_dir = "snapshots"
snapshot.assert_match(
        json.dumps(response.json(), indent=2, sort_keys=True),
        "endpoint_response"
    )

Best Practices for Snapshots

1. Use descriptive names: "user_list_response" not "response1"
2. Sort JSON keys: Ensures consistent snapshots
3. Format JSON: Use indent=2 for readable diffs
4. Exclude dynamic data: Remove timestamps, IDs, etc. that change between runs

Example of excluding dynamic data:

response_data = response.json()
# Remove dynamic fields for snapshot
response_data.pop("created_at", None)
response_data.pop("id", None)

snapshot.snapshot_dir = "snapshots"
snapshot.assert_match(
    json.dumps(response_data, indent=2, sort_keys=True),
    "static_response_data"
)

Writing Tests for API Routes

Basic Structure

import json
import fastapi
import fastapi.testclient
import pytest
from pytest_snapshot.plugin import Snapshot

from backend.api.features.myroute import router

app = fastapi.FastAPI()
app.include_router(router)
client = fastapi.testclient.TestClient(app)

def test_endpoint_success(snapshot: Snapshot):
    response = client.get("/endpoint")
    assert response.status_code == 200
    
    # Test specific fields
    data = response.json()
    assert data["status"] == "success"
    
    # Snapshot the full response
    snapshot.snapshot_dir = "snapshots"
    snapshot.assert_match(
        json.dumps(data, indent=2, sort_keys=True),
        "endpoint_success_response"
    )

Testing with Authentication

For the main API routes that use JWT authentication, auth is provided by the autogpt_libs.auth module. If the test actually uses the user_id, the recommended approach for testing is to mock the get_jwt_payload function, which underpins all higher-level auth functions used in the API (requires_user, requires_admin_user, get_user_id).

If the test doesn't need the user_id specifically, mocking is not necessary as during tests auth is disabled anyway (see conftest.py).

Using Global Auth Fixtures

Two global auth fixtures are provided by backend/api/conftest.py:

• mock_jwt_user - Regular user with test_user_id ("test-user-id")
• mock_jwt_admin - Admin user with admin_user_id ("admin-user-id")

These provide the easiest way to set up authentication mocking in test modules:

import fastapi
import fastapi.testclient
import pytest
from backend.api.features.myroute import router

app = fastapi.FastAPI()
app.include_router(router)
client = fastapi.testclient.TestClient(app)

@pytest.fixture(autouse=True)
def setup_app_auth(mock_jwt_user):
    """Setup auth overrides for all tests in this module"""
    from autogpt_libs.auth.jwt_utils import get_jwt_payload

    app.dependency_overrides[get_jwt_payload] = mock_jwt_user['get_jwt_payload']
    yield
    app.dependency_overrides.clear()

For admin-only endpoints, use mock_jwt_admin instead:

@pytest.fixture(autouse=True)
def setup_app_auth(mock_jwt_admin):
    """Setup auth overrides for admin tests"""
    from autogpt_libs.auth.jwt_utils import get_jwt_payload

    app.dependency_overrides[get_jwt_payload] = mock_jwt_admin['get_jwt_payload']
    yield
    app.dependency_overrides.clear()

The IDs are also available separately as fixtures:

• test_user_id
• admin_user_id
• target_user_id (for admin <-> user operations)

Mocking External Services

def test_external_api_call(mocker, snapshot):
    # Mock external service
    mock_response = {"external": "data"}
    mocker.patch(
        "backend.services.external_api.call",
        return_value=mock_response
    )

    response = client.post("/api/process")
    assert response.status_code == 200

    snapshot.snapshot_dir = "snapshots"
    snapshot.assert_match(
        json.dumps(response.json(), indent=2, sort_keys=True),
        "process_with_external_response"
    )

Best Practices

1. Test Organization

• Place tests next to the code: routes.py → routes_test.py
• Use descriptive test names: test_create_user_with_invalid_email
• Group related tests in classes when appropriate

2. Test Coverage

• Test happy path and error cases
• Test edge cases (empty data, invalid formats)
• Test authentication and authorization

3. Snapshot Testing Guidelines

• Review all snapshot changes carefully
• Don't snapshot sensitive data
• Keep snapshots focused and minimal
• Update snapshots intentionally, not accidentally

4. Async Testing

• Use regular def for FastAPI TestClient tests
• Use async def with @pytest.mark.asyncio for testing async functions directly

5. Fixtures

Global Fixtures (conftest.py)

Authentication fixtures are available globally from conftest.py:

• mock_jwt_user - Standard user authentication
• mock_jwt_admin - Admin user authentication
• configured_snapshot - Pre-configured snapshot fixture

Custom Fixtures

Create reusable fixtures for common test data:

@pytest.fixture
def sample_user():
    return {
        "email": "[email protected]",
        "name": "Test User"
    }

def test_create_user(sample_user, snapshot):
    response = client.post("/users", json=sample_user)
    # ... test implementation

Test Isolation

All tests must use fixtures that ensure proper isolation:

• Authentication overrides are automatically cleaned up after each test
• Database connections are properly managed with cleanup
• Mock objects are reset between tests

CI/CD Integration

The GitHub Actions workflow automatically runs tests on:

• Pull requests
• Pushes to main branch

Snapshot tests work in CI by:

1. Committing snapshot files to the repository
2. CI compares against committed snapshots
3. Fails if snapshots don't match

Troubleshooting

Snapshot Mismatches

• Review the diff carefully
• If changes are expected: poetry run pytest --snapshot-update
• If changes are unexpected: Fix the code causing the difference

Async Test Issues

• Ensure async functions use @pytest.mark.asyncio
• Use AsyncMock for mocking async functions
• FastAPI TestClient handles async automatically

Import Errors

• Check that all dependencies are in pyproject.toml
• Run poetry install to ensure dependencies are installed
• Verify import paths are correct

Summary

Snapshot testing provides a powerful way to ensure API responses remain consistent. Combined with traditional assertions, it creates a robust test suite that catches regressions while remaining maintainable.

Remember: Good tests are as important as good code!