https://issues.dlang.org/show_bug.cgi?id=20979

          Issue ID: 20979
           Summary: Which compiler is used by test/run.d?
           Product: D
           Version: D2
          Hardware: All
                OS: All
            Status: NEW
          Severity: normal
          Priority: P1
         Component: dmd
          Assignee: nobody@puremagic.com
          Reporter: bugzilla@digitalmars.com

1. how is the compiler version that is used to build test/run.d determined?

2. how is the compiler version that runs the test(s) determined?

3. how is the import path to druntime/phobos set for (1) and (2) ?

This documentation should be in test/run.d or test/README.md

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