How do I get code coverage report ONLY for specified tests in simplecov?

Question

I namespace my Rails 6 app into three parts and I want to run the code coverage only for a specific namespace like

$ rails test test/controllers/office
$ rails test test/controllers/member
$ rails test test/controllers/provider

SimpleCov currently shows the coverage of the whole project. I want to see the coverage report only for the specified tests.

I do not find any (direct) documentation. Closest thing is simplecov's profile but it

• needs profile name (hard-coded or env variable)
• accepts only one profile
• requires configured profiles
• does not relate with specified tests

How can I achieve code coverage report ONLY for the specified tests?

• Is there any existing way with simplecov?
• Is there any other alternative to simplecov to achieve what I want?

UPDATE:

simplecov has these directly related but open issues

• Report only on files in a given directory or matching a given glob #696
• Feature: generate coverage only for specific file under test #869
• Clarify relation between track_files and add_filter #610

UPDATE 2:

simplecov currently

• uses track_file method that accepts file pattern (set to {app,lib}/**/*.rb for rails profile)
• use the file pattern to calculate coverage