Touca's vision for the future of regression testing

We are excited to be launching Touca today: an automated regression testing system that helps engineering teams compare different versions of their software workflows and identify differences in behavior and performance.

Pejman Ghorbanzade
Pejman Ghorbanzade
May 26, 2021
6 Min

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We are excited to be sharing Touca with you today: an automated regression testing system that helps engineering teams compare different versions of their software workflows and identify differences in behavior and performance.

We want to reduce the risk of making code changes to mission-critical software components. We think our product can greatly benefit businesses building technologies like medical and financial software, machine learning algorithms, robotics, and autonomous driving systems.

A screenshot of the Touca Server showing differences found between different versions of a given software workflow.
Touca can show differences compare to a trusted version of your software.

Touca started as a side project when I was working at a medical imaging software company. We had to regularly test our software workflows with thousands of test cases to ensure the safety and accuracy of our product. Our test process was so long and labor-intensive that, sometimes, it took days to gain confidence that a recent code change had no unintended side effects. This long feedback cycle made the entire development process inefficient. Sometimes we decided against making necessary changes to certain components just because it was too difficult to retest them.

This problem is not specific to one company. Most software in industries like finance, medical, AI, and robotics have similarly laborious testing processes and are in the most need for automated regression testing. But there appears to be no clear solution that meets the requirements of these software. So I started Touca, with a mission to make maintaining software 10x more efficient.

Touca helps you continuously test complex algorithms with any number of real-world inputs. It offers client libraries that let you describe the behavior and performance of your workflow, for each test case. The libraries submit this information to a remote Touca Server that compares them with previously submitted results and reports discovered differences in real-time so that you can inspect them and take appropriate action.

Our approach solves common frustrations with using snapshot testing at scale. Unlike snapshot testing frameworks that store the output of workflows for each input into files and check those output files into version control systems, Touca handles all test results remotely, preserves all data types for lossless comparison, and gives full control over what variables you track, regardless of whether they are exposed through the interface.

Touca Product Launch and Demo


Touca enables you to do the following:

  • Create easy-to-automate regression test tools in minutes
  • Decouple your test cases from your test logic
  • Inspect your test results as test cases are executed

You can do all the above (and much more) without the need to compare or manage any test results. They are submitted to a self-hosted or cloud-hosted Touca server, accessible to all members of your team.

"We use Touca to perform nightly regression tests of our critical workflows. When we make changes to complex software, we need to have confidence that there have been no unexpected consequences. Touca gives us that confidence by tracking millions of output values computed from thousands of input datasets and helping us understand exactly how those outputs have changed from one build to the next. That confidence gives us leverage to develop new features faster and with fewer problems."
- Ben Jackson, Principal Software Engineer at Vital Images, Inc.

Current limitations

We want to disclose one important limitation in the service that we are launching today: While the Touca server is language agnostic, as of today, we only provide one open-source SDK for C++. We wanted to start with a language in which most existing mission-critical systems are written. Touca SDK for Python is scheduled for release in June. We plan to release SDKs for Java and JavaScript later this year.

Screenshot of Touca Server listing the test cases in a given version of a software.
Touca provides comparison results as your tests are executed.

Our vision

We want to significantly reduce the risk of making code changes to critical software components. By automating the execution of component-level tests, and the submission, processing, and management of their results, we want to reduce the manual effort required to gain confidence in new code changes. We think a shorter development feedback cycle makes maintaining software much more efficient.

There are three fundamental ideas to our approach.

Remote hosting and processing

Leave only the decision-making to software engineers. The distinctive feature of our solution is provisioning a dedicated service for the storage and processing of regression test results. This approach unlocks opportunities that were not available in traditional regression testing methods that dealt with test results as static files.

The remote server, deployed on cloud or on-premise, can process data once, and make the results available to all members of the team. With access to the submitted test results for different versions, it can provide insights into how the software evolves. It can detect brittle tests and let engineers handle them by defining custom comparison rules. By performing deep analysis of the submitted data, the server can effectively work as an assistant to the members of the engineering team, saving them time when interpreting the results.

Building software is teamwork. We think testing should be too. We notify engineers of new differences and provide a platform for them to work together in interpreting those differences and share comments and notes in the process. If differences are approved, we notify the team to ensure they have an up-to-date understanding of how their software is supposed to work.

Through integration with test execution servers, we can help teams trigger one-time or recurring execution of their test cases through the server, eliminating the manual efforts required to run them.

Separation of test cases from the test logic

Maintaining test code shouldn’t be a chore. When writing unit tests, software engineers are generally required to specify hard-coded expected values for each test case. This common practice requires that a change in system behavior is followed by adjustments of the expected values. This is because the input to functions under test is closely coupled with the logic of the test: i.e. the unit test code has hard-coded references to the input.

With Touca, the test cases are fully decoupled from the test logic. With no need to set expected values, the test logic of a typical regression test can simply invoke the code under test, one input at a time. Unlike unit tests, changes to system requirements do not necessarily need changing the test logic.

We can go one step further and manage the test cases entirely through the remote server. This way, team members can add notes to each test case and group them through setting tags (e.g. “smoke test”) if they like to execute each group separately.

Real-time feedback

Show the true impact of any code change during the development process: We want to empower engineers to have full visibility on how their changes impact the behavior and performance of their software. The faster we can provide this insight, the more time and effort we can save from software engineers. Such insight significantly reduces the likelihood of discovered defects in further stages of the development cycle.

We think we can provide this insight in near real-time. We can leverage our historical insight of previously submitted data to identify test cases with higher chances of regression and prioritize their execution.

We can also go further in making this real-time feedback more valuable by adding context to new differences such as including potentially relevant recent code changes. We have many ideas for improving the overall developer experience and will share them as we get closer to their implementation.

Next steps

We are just starting our journey towards making maintaining software 10x more efficient. We acknowledge that this journey would be long and that we have so much to learn in the process.

We don't think that any tool can independently solve software testing. As long as software is developed by humans, they will be the first and last decision makers on the quality of the product. But we believe that we have only scratched the surface of how automation tools can help them make the right decisions, faster and easier.

We look forward to solving interesting problems that can make life a little easier for software engineers building and maintaining complex products.

Thank you to Alex Plugaru, Beyang Liu, Daniel Feldman, Ivan Huerta, Nicolas Carlo, Titus Winters, and many others for reading drafts of this post.

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