When consuming the module, it imports the main branch of the maester-tests repo, which isn't tagged and I believe uses trunk based branching strategy?
This leads to a mismatch in the version of maester imported from the PowerShell Gallery, where the stable version of Maester can't find the functions from tests as they don't exists.
To get it to work, I had update the auto generate pipeline, adding the -AllowPrerelease to the import-module cmdlet.
I'd suggest that the tests repo should be tagged accordingly and the TF module be configured to require a version of Maester to be specified so everything can be aligned.