Regression test for https://github.com/zopefoundation/zope.testrunner/issues/6: when the test suite changes the current working directory, subprocess invocation might fail.

>>> import os.path, sys
>>> directory_with_tests = os.path.join(this_directory, 'testrunner-ex-6')
>>> defaults = [
...     '--path', os.path.relpath(directory_with_tests),
...     '--tests-pattern', '^cwdtests?$',
...     ]
>>> orig_cwd = os.getcwd()
>>> sys.argv = [os.path.relpath(testrunner_script), '-j2']
>>> from zope import testrunner
>>> testrunner.run_internal(defaults)
Running cwdtests.Layer1 tests:
  Set up cwdtests.Layer1 in 0.000 seconds.
  Ran 1 tests with 0 failures, 0 errors and 0 skipped in 0.000 seconds.
Running cwdtests.Layer2 tests:
  Running in a subprocess.
  Set up cwdtests.Layer2 in 0.000 seconds.
  Ran 1 tests with 0 failures, 0 errors and 0 skipped in 0.000 seconds.
  Tear down cwdtests.Layer2 in 0.000 seconds.
Tearing down left over layers:
  Tear down cwdtests.Layer1 in 0.000 seconds.
Total: 2 tests, 0 failures, 0 errors and 0 skipped in 0.162 seconds.
False
>>> os.chdir(orig_cwd)