Now I have this kind of workaround:

<!-- unit testing workaround -->
<Invoke Phase="Test" Class="Company.UnitTest.IPM" Method="Load" CheckStatus="true">
  <Arg>${root}/test</Arg>
</Invoke>
<Invoke Phase="Test" Class="Company.UnitTest.IPM" Method="RunTestPackage" CheckStatus="true">
  <Arg>CompanyTests</Arg>
</Invoke>

The amount of boilerplate is tolerable.

Test cases are located in ${root}/test.

Company.UnitTest.IPM is just an IPM "compatible" facade for our framework.

Now I can run test -o my-company-module. This has been working fine so far, fingers crossed there is no nasty surprises just waiting around the corner ...

I had a look into the IPM source code and I guess the correct places where the testing action happens are:

• %ZPM.PackageManager.Developer.Processor.UnitTest (OnPhase method)
• %ZPM.PackageManager.Developer.UnitTest.Manager

However I got a quite confused how I would be able to inject my own Processor.UnitTest and/or UnitTest.Manager there and what are those pParams that are passes everywhere.

Nexus is not listed in https://oras.land/adopters/ but OCI support is mentioned e.g. here: https://www.sonatype.com/blog/sonatype-nexus-repository-as-a-container-r...

Open Container Initiative (OCI) support

Sonatype Nexus Repository supports the Open Container Initiative
for creating open industry standards on container formats and runtime specifications. This lightweight, open governance structure provides guidance and continued growth across all leaders in the container industry.