Regression Testing in FPGA Development

Regression testing is a method of re-running test cases to make sure that everything still works after new changes have been made. Although some think it only applies to software, it is also very important in FPGA development. FPGAs use hardware description languages like VHDL or Verilog, but they still require quick development, frequent updates, and high-quality outcomes. When several developers add new code changes close together, there is a higher chance of introducing new errors or bringing back old issues. That is why regression testing, used alongside Continuous Integration (CI), is important. It helps confirming that the entire design remains stable whenever new code is committed to version control.

Importance of regression testing

Regression testing means re-running established tests to verify that the design remains correct after each change. In FPGA development, this means checking that everything still works as expected when there are changes to the code or configuration. Catching errors early helps developers fix them long before the design is placed on a physical FPGA or shared for broader testing.

Because many FPGA projects aim for faster delivery and frequent prototyping, CI tools such as Jenkins, GitLab CI, or Github Actions are often used. In a typical CI setup for FPGA projects, the design is built and simulated automatically for every code change. This helps in detecting errors early and reducing the chance of big problems later in the project.

Regression tests are the foundation of this process. They repeatedly confirm that parts of the design which worked before are still functioning correctly when new changes are introduced. As a result, developers can quickly see and fix potential issues.

Strategies for effective regression testing

One helpful approach is to focus on the most critical parts of the design first. You can run tests for these vital areas more often. Some developers run a small, fast set of tests for every code commit, while they save larger, slower test suites for specific milestones or scheduled runs. Where possible, developers can also run tests in parallel to speed up the process and reveal errors quickly.

HDLRegression

HDLRegression is a tool that we have made to help organise and automate regression testing for HDL code. With HDLRegression, you can clearly define testbenches and test cases, and the tool works with several simulators and can be run from the command line or in a CI pipeline. It also provides good reports on test results, allowing multiple developers to quickly see which tests have failed and address issues.

Conclusion

Regression testing in FPGA development helps ensure that ongoing changes do not reduce design quality or stability. By running tests often and automatically through a CI pipeline, the developer quickly knows if something has broken. This promotes smaller, more frequent code changes instead of large, infrequent ones that can be harder to fix. Finding problems early also saves time and money, making it easier to add new features without breaking existing functionality. By combining a clear testing strategy, the right tools, and active maintenance of test cases, developers can deliver FPGA designs that remain stable and predictable.

#FPGA #ASIC #UVVM #HDLRegression #Embedded #CI Inventas