Is there a way to create a global variable that would be scoped to a test run?

[gajus]

We need to set a global (unique) value for each test run, i.e. unique test execution ID.

I cannot think of what mechanism could work for this.

gobal.TEST_ID = uuid() would only work in --serial mode.

[novemberborn]

If I'm understanding this correctly, you have a test file with multiple test() calls, each calling shared code that needs to access a global variable, yet you want that variable to hold a different value for code invoked from separate tests?

This would work with serial tests (test.serial()) or synchronous test() calls. It becomes impossible for asynchronous tests unless perhaps you use https://nodejs.org/api/async_context.html#class-asynclocalstorage.