In Manager/Maestro 21.05 how do you determine if the form is in Test Mode?

We used to use Form.getSystemData("TestMode") to determine if a form is in TestMode, but this element no longer seems to be in the system profile?

Then, I thought I could add it using a Form Open Function, but I have not been able to find a way to access the TestMode flag with a fluent API.

Am I missing something, was a useful thing to be able to do.