Testing#

Testing is important for ensuring your code behaves as expected under various conditions. After creating a BentoML project, you can design different tests to verify both the functionality of the machine learning (ML) model and the operational aspects of the Service.

Testing provides multiple benefits, including:

  • Reliability: Ensure your BentoML Service behaves as expected, increasing confidence in the its stability.

  • Regularity: Facilitate regular and automated checking of the codebase for errors, helping catch issues early in the development cycle.

  • Refactorability: Make the codebase more maintainable and adaptable to change, as tests provide a safety net for modifications.

This document explains how to design and run tests for BentoML Services. It uses the Summarization Service in Quickstart as an example for testing.

Prerequisites#

Tests can be run using a test runner like pytest. Install pytest via pip if you haven’t already:

pip install pytest

For more information, see the pytest documentation.

Service verification#

After you create a service.py file, you can use a simple and straightforward verification script to quickly ensure that your Service is functioning as expected. This is ideal for use in a Jupyter Notebook or similar environments, allowing you to interactively debug and verify code changes during the development process. Here’s how you can implement it:

service_verification.py#
from service import Summarization, EXAMPLE_INPUT # Imported from the Summarization service.py file

# Initialize the Service
svc = Summarization()

# Invoke the Service with example input and print the output
output = svc.summarize(EXAMPLE_INPUT)
print(output)

This verification test provides immediate feedback by initializing the Service and loading the model into memory, which helps you verify that all components of the Service, including external dependencies and the model itself, are correctly set up.

If the model is too large or requires GPU resources, running this test on a laptop or in environments with limited resources (for example, GitHub Actions) might not be feasible. In such cases, you could connect to a remote GPU machine or utilize a Jupyter Notebook hosted on a server with adequate resources. For situations where loading the model is not practical, read the Unit tests section below to use mocking techniques to simulate model inference.

Unit tests#

Unit tests verify the smallest testable parts of a project, such as functions or methods, in isolation from the rest of the code. The purpose is to ensure that each component performs correctly as designed.

When dealing with ML models or Services like Summarization, where the output might not be exactly fixed, you can mock dependencies and output, and focus on testing the behavior and logic of the Service code rather than the model’s output. You might not test the model’s output directly but ensure that the BentoML Service interacts correctly with the model pipeline and processes inputs and outputs as expected.

An example:

test_unit.py#
from unittest.mock import patch, MagicMock
from service import Summarization, EXAMPLE_INPUT # Imported from the Summarization service.py file


@patch('service.pipeline')
def test_summarization(mock_pipeline):
    # Setup a mock return value that resembles the model's output structure
    mock_pipeline.return_value = MagicMock(return_value=[{"summary_text": "Mock summary"}])

    service = Summarization()
    summary = service.summarize(EXAMPLE_INPUT)

    # Check that the mocked pipeline method was called exactly once
    mock_pipeline.assert_called_once()
    # Check the type of the response
    assert isinstance(summary, str), "The output should be a string."
    # Verify the length of the summarized text is less than the original input
    assert len(summary) < len(EXAMPLE_INPUT), "The summarized text should be shorter than the input."

This unit test does the following:

  1. Use unittest.mock.patch to mock the pipeline function from the Transformers library.

  2. Create a mock object that simulates the behavior of the callable object returned by the real pipeline function. Whenever this mock callable object is called, it returns a list containing a single dictionary with the key "summary_text" and value "Mock summary". For more information, see mock object library.

  3. Make assertions to ensure the Service is functioning correctly.

Note

When the output is fixed and known (for example, a function that returns a constant value or a predictable result based on the input), you can write tests that directly assert the expected output. In such cases, mocking might still be used to isolate the function from any dependencies it has, but the focus of the test can be on asserting that the function returns the exact expected value.

Run the unit test:

pytest test_unit.py -v

Expected output:

====================================================================== test session starts ======================================================================
platform linux -- Python 3.11.7, pytest-8.0.2, pluggy-1.4.0 -- /home/demo/Documents/summarization/summarization/bin/python
cachedir: .pytest_cache
rootdir: /home/demo/Documents/summarization
plugins: anyio-4.3.0
collected 1 item

test_unit.py::test_summarization PASSED                                                                                                                   [100%]

======================================================================= 1 passed in 2.08s =======================================================================

Integration tests#

Integration tests assess the combined operation of two or more components. The goal is to ensure that different parts of your project work together as intended, including interactions with databases, external APIs, and other services.

Integration tests for a BentoML Service can involve starting the Service and sending HTTP requests to verify its response.

An example:

test_integration.py#
import bentoml
import subprocess

from service import EXAMPLE_INPUT # Imported from the Summarization service.py file

def test_summarization_service_integration():
    with subprocess.Popen(["bentoml", "serve", "service:Summarization", "-p", "50001"]) as server_proc:
        try:
            client = bentoml.SyncHTTPClient("http://localhost:50001", server_ready_timeout=10)
            summarized_text = client.summarize(text=EXAMPLE_INPUT)

            # Ensure the summarized text is not empty
            assert summarized_text, "The summarized text should not be empty."
            # Check the type of the response
            assert isinstance(summarized_text, str), "The response should be a string."
            # Verify the length of the summarized text is less than the original input
            assert len(summarized_text) < len(EXAMPLE_INPUT), "The summarized text should be shorter than the input."
        finally:
            server_proc.terminate()

This integration test does the following:

  1. Use the subprocess module to start the Summarization Service in a separate process on port 50001.

  2. Create a client and send a request. server_ready_timeout=10 means the client will wait 10 seconds for the server to become ready before proceeding with the call.

  3. Make assertions to ensure the Service is functioning correctly.

Run the integration test:

pytest test_integration.py -v

Expected output:

====================================================================== test session starts ======================================================================
platform linux -- Python 3.11.7, pytest-8.0.2, pluggy-1.4.0 -- /home/demo/Documents/summarization/summarization/bin/python
cachedir: .pytest_cache
rootdir: /home/demo/Documents/summarization
plugins: anyio-4.3.0
collected 1 item

test_integration.py::test_summarization_service_integration PASSED                                                                                        [100%]

====================================================================== 1 passed in 19.29s =======================================================================

HTTP behavior tests#

To test the HTTP behavior of a BentoML Service, you can simulate HTTP requests and assert the responses match expected outcomes.

You can use the httpx library to create a test client. This allows you to send HTTP requests directly to your BentoML Service, which can be converted to an ASGI application via the to_asgi() method. The init parameter of to_asgi(), when set to true, initializes the middleware, routing, and other necessary configurations, preparing the application for handling requests.

An example:

test_http.py#
import httpx
from service import Summarization, EXAMPLE_INPUT # Imported from the Summarization service.py file
import pytest

@pytest.mark.asyncio
async def test_request():
    # Initialize the ASGI transport with the Summarization Service
    transport=httpx.ASGITransport(app=Summarization.to_asgi(init=True))

    async with httpx.AsyncClient(transport=transport, base_url="http://testserver") as test_client:
        response = await test_client.post("/summarize", json={"text": EXAMPLE_INPUT})
        # Retrieve the text from the response for validation
        summarized_text = response.text
        # Assert that the HTTP response status code is 200, indicating success
        assert response.status_code == 200
        # Assert that the summarized text is not empty
        assert summarized_text, "The summary should not be empty"

This test does the following:

  • Define a test function with @pytest.mark.asyncio, which allows the test to perform asynchronous operations.

  • Create an asynchronous HTTP client, which interacts with the ASGI application converted from the Summarization Service through to_asgi(init=True). base_url="http://testserver" configures the client to send requests to a test server.

  • Send a POST request to the /summarize endpoint. It simulates a client sending input data to the Summarization Service for processing.

  • Make assertions to ensure the Service is functioning correctly.

Run the HTTP behavior test:

pytest test_http.py -v

Note

You need a plugin like pytest-asyncio to run async tests. You can install it by running pip install pytest-asyncio.

Expected output:

================================================================================== test session starts ===================================================================================
platform linux -- Python 3.11.7, pytest-8.0.2, pluggy-1.4.0 -- /home/demo/Documents/summarization/summarization/bin/python
cachedir: .pytest_cache
rootdir: /home/demo/Documents/summarization
plugins: anyio-4.3.0, asyncio-0.23.5.post1
asyncio: mode=Mode.STRICT
collected 1 item

test_http.py::test_request PASSED                                                                                                                                                  [100%]

=================================================================================== 1 passed in 6.13s ====================================================================================

End-to-end tests#

End-to-end testing is important to ensure that your AI application not only performs well under controlled test conditions but also runs effectively in a live, production-like environment.

You can implement the following in your end-to-end test when deploying a BentoML Service to BentoCloud.

  1. Create a test Deployment: Deploy your BentoML Service to BentoCloud.

  2. Wait for Deployment readiness: Ensure the Deployment is fully ready to handle requests.

  3. Send test requests and verify output: Interact with the Deployment by sending test requests and validating the responses to ensure the Service is performing as expected.

  4. Shut down and delete the Deployment: Clean up by shutting down and deleting the test deployment to avoid unnecessary costs.

An example:

test_e2e.py#
import pytest
import bentoml
from service import Summarization, EXAMPLE_INPUT  # Imported from the Summarization service.py file

@pytest.fixture(scope="session")
def bentoml_client():
    # Deploy the Summarization Service to BentoCloud
    deployment = bentoml.deployment.create(
        bento="./path_to_your_project", # Alternatively, use an existing Bento tag
        name="test-summarization",
        scaling_min=1,
        scaling_max=1
    )
    try:
        # Wait until the Deployment is ready
        deployment.wait_until_ready(timeout=3600)

        # Provide the Deployment's client for testing
        yield deployment.get_client()
    finally:
        # Clean up
        bentoml.deployment.terminate(name="test-summarization")
        bentoml.deployment.delete(name="test-summarization")

def test_summarization_service(bentoml_client):
    # Send a request to the deployed Summarization service
    summarized_text: str = bentoml_client.summarize(text=EXAMPLE_INPUT)
    # Ensure the summarized text is not empty
    assert summarized_text, "The summarized text should not be empty."
    # Check the type of the response
    assert isinstance(summarized_text, str), "The response should be a string."
    # Verify the length of the summarized text is less than the original input
    assert len(summarized_text) < len(EXAMPLE_INPUT), "The summarized text should be shorter than the input."

This test does the following:

  • Set up the Deployment of the Summarization Service on BentoCloud with the bentoml_client fixture. It ensures the Deployment is created and ready before yielding a client for testing.

  • Use the client to interact with the Summarization Service and make assertions to ensure the Service is functioning correctly.

  • Clean up by terminating and deleting the Deployment after the test to prevent ongoing charges for unused resources.

Run the end-to-end test:

pytest test_e2e.py -v

Expected result:

=================================================================================================== test session starts ===================================================================================================
platform linux -- Python 3.11.7, pytest-8.1.1, pluggy-1.4.0 -- /home/demo/Documents/summarization/summarization/bin/python
cachedir: .pytest_cache
rootdir: /home/demo/Documents/summarization/test
plugins: anyio-4.3.0
collected 1 item

test_e2e.py::test_summarization_service PASSED                                                                                                                                                                      [100%]

============================================================================================== 1 passed in 120.65s (0:02:00) ==============================================================================================

For more information, see Configure Deployments and Manage Deployments.

Best practices#

Consider the following when designing your tests:

  • Keep unit tests isolated; mock external dependencies to ensure tests are not affected by external factors.

  • Automate tests using CI/CD pipelines to ensure they are run regularly.

  • Keep tests simple and focused. A test should ideally verify one behavior.

  • Ensure your testing environment closely mirrors your production environment to avoid “it works on my machine” issues.

  • To customize or configure pytest and make your testing process more efficient and tailored to your needs, you can create a pytest.ini configuration file. By specifying settings in pytest.ini, you ensure that pytest consistently recognizes your project structure and preferences across different environments and setups. Here is an example:

    [pytest]
    # Add current directory to PYTHONPATH for easy module imports
    pythonpath = .
    
    # Specify where pytest should look for tests, in this case, a directory named `test`
    testpaths = test
    
    # Optionally, configure pytest to use specific markers
    markers =
       integration: mark tests as integration tests.
       unit: mark tests as unit tests.
    

    Navigate to the root directory of your project (where pytest.ini is located), then run the following command to start testing:

    pytest -v
    

    Expected output:

    ================================================================================== test session starts ===================================================================================
    platform linux -- Python 3.11.7, pytest-8.0.2, pluggy-1.4.0 -- /home/demo/Documents/summarization/summarization/bin/python
    cachedir: .pytest_cache
    rootdir: /home/demo/Documents/summarization
    configfile: pytest.ini
    testpaths: test
    plugins: anyio-4.3.0, asyncio-0.23.5.post1
    asyncio: mode=Mode.STRICT
    collected 3 items
    
    test/test_http.py::test_request PASSED                                                                                                                                             [ 33%]
    test/test_integration.py::test_summarization_service_integration PASSED                                                                                                            [ 66%]
    test/test_unit.py::test_summarization PASSED                                                                                                                                       [100%]
    
    =================================================================================== 3 passed in 17.57s ===================================================================================