Test XLA examples (#5583)

* Test XLA examples

* Style

* Using `require_torch_tpu`

* Style

* No need for pytest

src/transformers/testing_utils.py

@@ -2,7 +2,7 @@ import os
 import unittest
 from distutils.util import strtobool
 
-from transformers.file_utils import _tf_available, _torch_available
+from transformers.file_utils import _tf_available, _torch_available, _torch_tpu_available
 
 
 SMALL_MODEL_IDENTIFIER = "julien-c/bert-xsmall-dummy"
@@ -113,6 +113,16 @@ def require_multigpu(test_case):
     return test_case
 
 
+def require_torch_tpu(test_case):
+    """
+    Decorator marking a test that requires a TPU (in PyTorch).
+    """
+    if not _torch_tpu_available:
+        return unittest.skip("test requires PyTorch TPU")
+
+    return test_case
+
+
 if _torch_available:
     # Set the USE_CUDA environment variable to select a GPU.
     torch_device = "cuda" if parse_flag_from_env("USE_CUDA") else "cpu"