[testing] replace hardcoded paths to allow running tests from anywhere (#6523)

* [testing] replace hardcoded paths to allow running tests from anywhere

* fix the merge conflict

src/transformers/testing_utils.py

@@ -1,3 +1,4 @@
+import inspect
 import os
 import re
 import shutil
@@ -144,6 +145,15 @@ def require_torch_and_cuda(test_case):
         return test_case
 
 
+def get_tests_dir():
+    """
+    returns the full path to the `tests` dir, so that the tests can be invoked from anywhere
+    """
+    # this function caller's __file__
+    caller__file__ = inspect.stack()[1][1]
+    return os.path.abspath(os.path.dirname(caller__file__))
+
+
 #
 # Helper functions for dealing with testing text outputs
 # The original code came from: