Sigasi Studio VUnit Integration

[Only in Sigasi Studio XPRT]

VUnit  is an open source unit testing framework for VHDL and SystemVerilog. VUnit helps you to write tests more easily and run them frequently.

Sigasi Studio can help you manage VUnit projects and enables you to run and inspect test results straight from the IDE.

When you import a VUnit project or add VUnit support to an existing project, Sigasi Studio runs VUnit in the background and automatically adds the correct libraries - as specified by the VUnit script - to your project. It also shows error markers in the VUnit script ( if anything goes wrong.

Since Sigasi Studio 4.14, the library mapping of the project is automatically updated based on the contents of the VUnit script.

VUnit project

VUnit project setup in Sigasi Studio


VUnit version 4.5.0 or higher is required.

Sigasi Studio needs to know where VUnit is installed. If you installed VUnit using pip install vunit_hdl and Python is in your path, then Sigasi Studio should find your VUnit installation. To verify whether Sigasi Studio can find your VUnit installation, go to Window > Preferences > Sigasi > Toolchains > VUnit and check the read-only VUnit installation path field.

If your Python installation is not in the path, you can configure it here in the Python executable location field.

If you have installed VUnit in a dedicated location, you should add the VUnit location to the $PYTHONPATH and make sure the $PYTHONPATH variable is visible to Sigasi Studio.

When you’re installing VUnit in a virtualenv, make sure to launch Sigasi Studio from within the terminal after activating the virtualenv.

If you installed VUnit from the Microsoft Store, you might get an error message when trying to select the Python executable. To use Python outside of Windows Store apps, Python needs to be installed using an installer from .

You should make sure that the python --version command only returns the VUnit version number. Additional output will prevent Sigasi Studio to parse the VUnit version number correctly and will result in errors.

Import VUnit Project

To import an existing VUnit project, click File > Import… > Sigasi > Import a VUnit project. Next, select the VUnit script ( and the location for the Sigasi Project.

The VUnit project repository comes with a number of example projects  which can be imported this way. If you first specify the Python Script Location, the Project Location will be set automatically.

Add VUnit support to an existing Sigasi project

You can also add VUnit support to an existing project: Right-click your project and select Configure > Add VUnit support. Next, select an existing script or let Sigasi create an example script.

VUnit project

VUnit project configuration and troubleshooting

The VUnit integration in Sigasi Studio gives useful feedback in the VUnit Console View. To open this view, first open a console (Window > Show View > Other… > General > Console) and in the Console View toolbar click the triangle () next to the Open Console icon. Select VUnit Console to open the VUnit Console View.

Since Sigasi Studio 4.14, the library configuration from is used to configure the library configuration in the Sigasi Studio project.

Note that this automatic configuration does not work with linked folders. You need to manually assign linked folders or any files/folders in them to a library.

Path separators in the file need a /, also on Windows.


For SystemVerilog projects you need to manually add the VUnit include files to your projects:

  • Right click your project, select New > Folder > Advanced > Link to alternate location and add VUNIT/verilog/include as location.
  • Use the Quick Fix on the failing `include "vunit_defines.svh" to add the include folder to the include paths.
Add verilog include path

Configure options for finding and running tests

In Window > Preferences > Sigasi > Toolchains > VUnit you can add different options for finding and running tests.

  • The options for finding tests will be passed to when generating the json file that lists the VUnit tests.
  • The options for running tests will be passed to when running the VUnit tests.
  • Select Set VUnit output to project root to have the VUnit output stored in the project root instead of in the temp location from where VUnit is called.
VUnit preferences dialog

Configuring the simulator

VUnit makes use of an external simulator to run tests. ActiveHDL, RivieraPRO, GHDL, and ModelSim/QuestaSim are all supported. By default, VUnit will try to find one of these simulators on your system and will use the first one found.

If you want to use a particular simulator, you can set the VUNIT_SIMULATOR environment variable to one of activehdl, rivierapro, ghdl, or modelsim to specify which simulator to use. In Linux, set the environment variable prior to starting Sigasi Studio, either in your shell initialization scripts (e.g. .bashrc or .bash_profile for bash shell), or set the variable on the fly in your terminal window. In Windows, open the dialog Edit environment variables for your account to set VUNIT_SIMULATOR.

You may also need to set the PATH of the simulator to use. For this purpose, configure the appropriate environment variable for your simulator with the correct path: VUNIT_ACTIVEHDL_PATH, VUNIT_RIVIERAPRO_PATH, VUNIT_GHDL_PATH, or VUNIT_MODELSIM_PATH. For example:

export VUNIT_RIVIERAPRO_PATH=/eda/Aldec/Riviera-PRO-2022.04-x64/bin

Finally, it is also possible to configure the simulator in, as shown below.

# Some code omitted

# Select simulator before calling VUnit.from_argv !
os.environ["VUNIT_SIMULATOR"] = "rivierapro"
# Optionally set the PATH
#os.environ["VUNIT_RIVIERAPRO_PATH"] = "/path/to/simulator/bin"

vu = VUnit.from_argv()

# More code omitted

For more information on simulator selection, check out the VUnit website .

Run VUnit Tests

There are multiple ways to run VUnit tests in Sigasi Studio:

  • Right click your project and select Run VUnit tests to run all tests in your project.
  • Right click one or more HDL files and select Run VUnit tests to run all tests in the selected files.
  • Right click in the Sigasi editor and select Run VUnit tests to run all tests in the active editor.
  • Right click in the VUnit test name (the string in the run function call) and select Run VUnit test to run this single test only.
  • Rerun the tests in the VUnit view.
Run VUnit VHDL tests

Inspect VUnit Test Results

When you run VUnit tests in Sigasi Studio, the VUnit view is opened. This view presents a convenient way to inspect the test results.

VUnit SystemVerilog Example

You can inspect the entire VUnit output in the Console view.

Handling specific common libraries

In Sigasi Studio, Common Libraries may be present in a project. Some of these are standardized and available in all tools, e.g. IEEE VHDL libraries, or the VUnit library in case of a VUnit project. Your project may also require vendor or company specific common libraries. External simulators, including the simulator which runs your VUnit tests, require a particular setup to find your library.

If, for instance, ModelSim is used, then:

  • common libraries need to be pre-compiled,
  • a customized modelsim.ini with a reference to the pre-compiled libraries is required, and
  • VUnit needs to be aware of the customized modelsim.ini.

The latter is achieved by setting an environment variable VUNIT_MODELSIM_INI which points at the customized modelsim.ini. One could set this variable from the shell (Linux) or user variables (Windows), but that is inconvenient as all projects will use the same modelsim.ini. A better solution is to set VUNIT_MODELSIM_INI in the script, before calling VUnit.from_argv().

# This is
# code omitted
os.environ['VUNIT_MODELSIM_INI'] = '/path/to/custom/modelsim.ini'
vu = VUnit.from_argv()
# code omitted

Note that VUnit may still produce warnings that the library is missing, as shown below. These warnings are harmless. They show up because only Sigasi Studio and the simulator are aware of the library, while VUnit is not.

WARNING - C:\Users\Wim Meeus\workspaceSigasi\VUnit-demo\design\design_top.vhd: failed to find library 'vucommon'

Alternatively, one could define the library and its contents in the script. In that case, VUnit will be aware of the library and the warnings won’t show, but compile times will be longer - which is exactly what common libraries are meant to avoid.

Using an external compiler in a VUnit project

If you want to configure an external compiler in a VUnit project (e.g. for additional syntax checking), you need to ensure that the compiler has the VUnit library. Otherwise, the compiler will flag all VUnit constructs in your HDL code as errors.

How to compile and enable the VUnit library for an external compiler is explained in the libraries section of this manual.