tst_qt_testrunner.py invokes qt_testrunner.py which invokes qt_mock_test.py. On Windows a python script is not directly executable. It needs to be executed as "python.exe script.py". To achieve that when testing, the tests set the env var QT_TESTRUNNER_TESTING. When qt-testrunner detects that, it prepends the command line with sys.executable which is the currently used python interpreter. Doing so also ensures that all sub-scripts are executed with the same Python version. Pick-to: 6.11 6.10 6.8 Change-Id: I4786e4015ded328077fd9cc7b443f4b4d9d69de7 Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io> Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>