Allow Tests To Run In Parallel

Optimizing Test Execution Time in Regal

With a large and growing codebase, such as the Regal project, comes the challenge of managing test execution time. As the number of unit tests increases, so does the time it takes to run them. In the case of Regal, with almost 700 unit tests, the test execution time has become noticeable, even on the fastest hardware. This is not a matter of slow performance, but rather a couple of seconds on the fastest hardware and many more in contexts like GitHub runners.

The Need for Parallel Testing

One obvious solution to this problem is to allow tests to run in parallel. This would enable the use of multiple CPU cores, where available, to speed up test execution. Rego tests are well-suited for parallelization, as they do not easily depend on state getting mutated between tests. However, a parallel implementation would require careful consideration of several factors.

Challenges in Parallelizing Tests

While parallelizing tests may seem like a straightforward task, there are several challenges that need to be addressed. Some of these challenges include:

• Test dependencies: Tests may depend on each other, either directly or indirectly, which can make parallelization more complex.
• Shared resources: Tests may share resources, such as databases or file systems, which can lead to conflicts when running tests in parallel.
• Test isolation: Tests may not be isolated from each other, which can lead to unexpected behavior when running tests in parallel.

A Parallel Implementation

To overcome these challenges, a parallel implementation would need to consider the following:

• Test grouping: Grouping tests into smaller sets, based on their dependencies or resources, can help to reduce conflicts and improve parallelization.
• Test prioritization: Prioritizing tests based on their importance or criticality can help to ensure that critical tests are run first.
• Resource management: Managing resources, such as databases or file systems, can help to prevent conflicts and ensure that tests run smoothly.

Opt-in Parallelism

A great first step in implementing parallelism would be to provide an option or opt-in to set the level of parallelism. This would allow developers to choose the level of parallelism that best suits their needs. Later, the default level of parallelism could be set to the number of cores available, like opa run, or a smart heuristic based on the number of tests to run.

Benefits of Parallel Testing

The benefits of parallel testing are numerous. Some of these benefits include:

• Faster test execution: Parallel testing can significantly reduce test execution time, making it easier to run tests and identify issues.
• Improved test coverage: Parallel testing can help to improve test coverage by allowing developers to run more tests in a shorter amount of time.
• Increased productivity: Parallel testing can help to increase productivity by reducing the time it takes to run tests and identify issues.

Conclusion

Optimizing Test Execution Time in Regal

Q&A: Parallel Testing in Regal

Q: What are the benefits of parallel testing in Regal?

A: The benefits of parallel testing in Regal include faster test execution, improved test coverage, and increased productivity. By running tests in parallel, developers can significantly reduce test execution time, making it easier to run tests and identify issues.

Q: How does parallel testing work in Regal?

A: In Regal, parallel testing works by running multiple tests simultaneously on multiple CPU cores. This is achieved through the use of a parallel testing framework that groups tests into smaller sets and runs them in parallel.

Q: What are the challenges of parallelizing tests in Regal?

A: Some of the challenges of parallelizing tests in Regal include test dependencies, shared resources, and test isolation. Tests may depend on each other, either directly or indirectly, which can make parallelization more complex. Additionally, tests may share resources, such as databases or file systems, which can lead to conflicts when running tests in parallel.

Q: How can I implement parallel testing in Regal?

A: To implement parallel testing in Regal, you can use a parallel testing framework that supports Regal. Some popular parallel testing frameworks for Regal include Testify and Ginkgo. These frameworks provide a simple and easy-to-use API for running tests in parallel.

Q: Can I customize the level of parallelism in Regal?

A: Yes, you can customize the level of parallelism in Regal. By using a parallel testing framework that supports Regal, you can set the level of parallelism to the number of cores available, like opa run, or a smart heuristic based on the number of tests to run.

Q: How can I measure the effectiveness of parallel testing in Regal?

A: To measure the effectiveness of parallel testing in Regal, you can use metrics such as test execution time, test coverage, and developer productivity. By tracking these metrics, you can determine whether parallel testing is improving test execution time and increasing productivity.

Q: Are there any best practices for implementing parallel testing in Regal?

A: Yes, there are several best practices for implementing parallel testing in Regal. Some of these best practices include:

• Test grouping: Grouping tests into smaller sets, based on their dependencies or resources, can help to reduce conflicts and improve parallelization.
• Test prioritization: Prioritizing tests based on their importance or criticality can help to ensure that critical tests are run first.
• Resource management: Managing resources, such as databases or file systems, can help to prevent conflicts and ensure that tests run smoothly.

Conclusion

In conclusion, parallel testing is a powerful tool for improving test execution time and increasing productivity in Regal. By understanding the benefits and challenges of parallel testing, implementing parallel testing in Regal, customizing the level of parallelism, measuring the effectiveness of parallel testing, and following best practices, developers can take advantage of parallel testing and improve their test execution time.