Separate Base And Extras Testing Environments

This article discusses the separation of testing environments for base functionality and optional extras in a software project, drawing from a conversation initiated in issue #254. The primary goal is to ensure that core functionalities are tested independently of optional extensions, leading to more robust and reliable software.

Introduction

The discussion revolves around managing dependencies and testing in a project where certain features are provided as optional extras. Specifically, the article addresses the transition of proxystore from a required dependency to an optional extra and the implications for testing.

The Need for Separate Environments

The core idea is to establish distinct testing environments: one for the base functionality without any extras, and another for testing with all extras installed. This approach has several benefits:

• Ensuring Core Functionality: By testing the base environment in isolation, we can guarantee that the fundamental features of the project work as expected, regardless of whether any extras are installed.
• Isolating Extra-Specific Issues: Separating the testing environments makes it easier to identify and resolve issues that are specific to certain extras, without being masked by problems in the base functionality.
• Improved Testability: It simplifies the testing process by allowing developers to focus on specific aspects of the project, such as the core features or the behavior of a particular extra.

Proposed Solution: Tox Environments

To implement the separation of testing environments, the proposal suggests using tox, a popular tool for automating testing in Python projects. The idea is to create separate tox environments for the base functionality and the extras.

Base Environment

The base tox environment would be configured to test the core functionality of the project without any extras installed. This environment would ensure that all essential features work as expected, regardless of the presence of any optional dependencies.

Extras Environment

In contrast, the extras tox environment would be set up to test the project with all extras installed. This environment would verify that the extras integrate correctly with the base functionality and that they provide the expected additional features. For example, a command like tox -e py313-extras or py313-full could be used to run tests in this environment, ensuring all extras are included.

Addressing Code Coverage

One of the key considerations when separating testing environments is how to handle code coverage. Code coverage is a metric that measures the percentage of code that is executed during testing. It's an important indicator of the thoroughness of the testing process.

Several options were discussed for addressing code coverage in the context of separate testing environments:

1. Excluding Files from Coverage: This approach involves excluding certain files from coverage in the base tox environment. This might be necessary if those files contain code that is only relevant when certain extras are installed.
2. Using a Coverage Plugin: A more sophisticated approach is to use a coverage plugin that can conditionally ignore modules based on whether their dependencies are installed. This would allow the coverage tool to accurately reflect the code that is being executed in each environment.
3. Focusing Coverage on the Full Environment: Another option is to only measure code coverage in the full test environment, where all extras are installed. This would simplify the coverage process, but it might not provide as much insight into the coverage of the base functionality.
4. Combining Coverage Reports: The most comprehensive approach involves setting up build artifacts in CI to upload the partial coverage reports from different test environments and then combining them into a single report. This would provide a complete picture of code coverage across all environments, but it would also be the most complex to implement.

Option Considerations

• Excluding Files: While straightforward, this option might not scale well if the number of extras increases significantly.
• Coverage Plugin: Offers a more dynamic solution but requires finding and configuring a suitable plugin.
• Full Environment Coverage: Simplifies the process but may overlook coverage gaps in the base functionality.
• Combined Reports: Provides the most comprehensive view but is the most complex to set up, especially for local runs.

Current Status and Future Considerations

Currently, the project only has one extra, proxystore, and the proxystore support in the project is isolated to a single module. As a result, the decision was made to defer the implementation of separate testing environments for now. This is because the benefits of separating the environments are not yet significant enough to justify the additional complexity.

However, the article acknowledges that this situation may change in the future as more integrations and testing complexities are added. In that case, it may become necessary to revisit the decision and implement separate testing environments to ensure the continued quality and reliability of the project.

Low Priority for Now

Given the current state, this task is considered a low priority. The focus remains on managing the existing setup and monitoring how things evolve as new integrations are introduced.

Conclusion

In conclusion, the separation of testing environments for base functionality and optional extras is a valuable strategy for ensuring the quality and reliability of software projects. While not always necessary, it can be particularly beneficial in projects with a growing number of optional dependencies and complex testing requirements. The decision of whether to implement separate testing environments should be based on a careful consideration of the project's specific needs and priorities. For more information on testing environments and best practices, you can check out resources like Mozilla's Testing Documentation.