VUnit - The Best Value for Initial Effort - Part 1

Best Value Part 1

This article was originally posted on LinkedIn where you may find some comments on its contents.

In the book Effective Coding with VHDL published this summer VUnit was presented as the most advanced testing framework of its kind.

For VHDL, the most advanced framework is VUnit

VUnit is the framework providing the most extensive set of features for full test automation and if you think of advanced as something being feature-rich this statement makes perfect sense. However, the word advanced can also be intimidating, indicating something that is hard to learn and use. We’ve always been very aware of this potential problem and worked hard to prevent the advanced features from messing up the simple stuff. The VUnit you see today is actually the third generation. The first two never made it to the public because we didn’t think the basic principles were simple enough. Don’t get me wrong, we want to be feature complete but equally important is the ease of getting started. This must also be true

For VHDL, VUnit gives the best value for initial effort

I think VUnit has achieved this and I will show why in a number of short blogs and video clips. The first clip is about installing VUnit. This is something that can be done in less than a minute.

When companies and individuals start using VUnit they take the path of least resistance. What that path is depends on the starting point but one common approach is the following.

  • Individuals start using VUnit on their own code and then it spreads among their colleagues. It’s much easier to get started and lead by example than trying to get an up-front corporate decision.

  • VUnit is initially used to fully automate testing for already existing and self-checking testbenches. There is no added value in replacing existing VHDL assert statements with the checks provided by VUnit even though they provide many more capabilities. These checks are introduced when developing new testbenches or when the old ones are refactored for some other reason.

  • VUnit is adopted in small bits and pieces. Why? Because you can and it’s much more convenient.

Based on this approach the upcoming blogs will present VUnit adoption in the following order

  • The second blog will show how you can create a single run script that provides automated and incremental compilation of all your project testbenches. This script is simulator vendor agnostic and is another one minute effort in my example project downloaded from opencores. The project consists of 18 VHDL files verified by 11 testbenches.

  • The third blog will show how 5 lines of code added to your testbenches will give you a fully automated test environment with a single call to the previously developed run script. Most projects will also experience a significant increase in simulation speed due to the multicore simulation support provided by VUnit (~4x on a quad core computer).

The steps above were less than 10 minutes of work for my example project. Much value for almost no initial effort and hardly without touching existing VHDL code.

I will then wrap up this getting started with VUnit blog series with

  • Developing and debugging with VUnit - Switching between working in the simulator GUI and using the run script.

  • Using test cases - Speed up the simulation even more.

  • Using VUnit configurations - Running your testbenches with different generics.

Comments and questions are encouraged. You can do it here on LinkedIn but I highly recommend using our user community chat room. It’s a better technical platform for Q&A but more important is that you will hear the voices of other users, not just the potentially single-sided opinions of the VUnit developers. We have different backgrounds, different skills, and different opinions so it becomes a much more interesting discussion.