What is VUnit?

VUnit is an open source unit testing framework for VHDL/SystemVerilog released under the terms of Mozilla Public License, v. 2.0. It features the functionality needed to realize continuous and automated testing of your HDL code. VUnit doesn’t replace but rather complements traditional testing methodologies by supporting a “test early and often” approach through automation.

VUnit reduces the overhead of testing by supporting automatic discovery of test benches and compilation order as well as including libraries for common verification tasks. It improves the speed of development by supporting incremental compilation and by enabling large test benches to be split up into smaller independent tests. It increases the quality of projects by enabling large regression suites to be run on a continuous integration server.

VUnit does not impose any specific verification methodology on its users. The benefits of VUnit can be enjoyed when writing tests first or last, when writing long running top level tests or short running unit tests, when using directed or constrained random testing. Often projects adopt mix of approaches for different testing needs. VUnit has been used in production environments where thousands of tests take several hours to run on powerful multi-core machines as well as in small open source projects where only a small package is tested in a few seconds.

Main Features

  • Python test suite runner that enables powerful test administration, can continue testing after fatal run-time errors (e.g. division by zero), and ensures test case independence.

  • Automatic scanning of files for tests, file dependencies, and file changes enable automatic (re)compilation and execution of test suites.

  • Can run test cases in parallel to take advantage of multi-core machines.

  • Support for running test benches with multiple generic/parameter settings.

  • Scriptable API as well as command line support.

  • Has --gui switch to launch test cases in the simulator GUI when debugging is necessary.

  • Assertion checker library that extends VHDL built-in support (assert).

  • Logging framework supporting display and file output, different log levels, visibility settings of levels and design hierarchy, output formatting and multiple loggers. Supports machine readable output formats that for example can be read by a spreadsheet.

  • Requirements trace-ability through JSON Export and test attributes.

  • Optional location preprocessor that traces log and check calls back to file and line number.

  • Outputs JUnit report files for better Jenkins integration.

  • Builds on the commonly used xUnit architecture.

Getting Started

There are a number of ways to get started.


Any bug reports, feature requests or questions about the usage of VUnit can be made by creating a new issue.

Credits and License

Substantial contributors are shown in the table below, but many others contributed with minor patches. Find a list at github.com/VUnit/vunit/graphs/contributors.

With apologies to anyone who ought to be either on this table or in the GitHub contributor list, but isn’t. Thanks also to all those who have reported bugs and support issues, and often patches and testcases.

Contributor 1


Asplund, Lars [@LarsAsplund] 2

Founder and main author of VUnit as a whole

Kraigher, Olof [@kraigher]

Founder and main author of VUnit until v4

Marquardt, Colin [@cmarqu]

Cadence Incisive support

Martinez-Corral, Unai [@umarcor] 2

Continuous Integration (CI), Co-simulation with GHDL’s VHPIDIRECT interface (VUnit/cosim, based on ghdl/ghdl-cosim)

Siluk, Sławomir [@slaweksiluk]

Verification Components (such as Avalon and Wishbone)


In alphabetical order



VUnit, except for the projects below, is released under the terms of Mozilla Public License, v. 2.0. © 2014-2021 Lars Asplund, lars.anders.asplund@gmail.com.

The following libraries are redistributed with VUnit for convenience:

The font used in VUnit’s logo and illustrations is ‘Tratex’, the traffic sign typeface used on swedish road signs: