No. This is not correct. I believe that an OS-level Process (=Java VM instance) is forked per Test Suite in a Test Suite Collection. I have got an evidence.
I have made a project published on GitHub:
In this project, you will find a Test Suite Collection named “TSC_usingTimestampedLogger” which binds 4 Test Suites and execute them in parallel mode. I executed the TSC and monitored Activity Monitor on Mac to see how OS-level processes behave.
When I executed the TSC, I could see 4 “java” processes are newly forked and finished just in sync with 4 Test Suites in the TSC started and finished. The following screenshot shows it.
If Test Suites in parallel mode run in Java Threads, I should have never observed OS-level Processes being forked.