When it will be possible to run testing environment?

Hello, 
I tried to google out the answer for my issue, and I found exact issue here: Session issue with CI Environment set to Testing (CI4) (codeigniter.com)
However, proposed solution to use "test" instead of "testing" is not valid (because CI then shows "The application environment is not set correctly."). I've set all params for testing environment according to documentation, it connects to DB successfully, however, session is never written to db. $_SESSION parameter also empty after each refresh. If I set environment to DEVELOPMENT or PRODUCTION - everything is fine. I couldn't believe that there is a known bug and nobody addresses it for a half year, there should be at least someone who used CI4 on testing environment. When this bug will be solved?