[testing] add timeout_decorator (#3543)

tests/test_modeling_bart.py

@@ -13,10 +13,11 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-
 import tempfile
 import unittest
 
+import timeout_decorator  # noqa
+
 from transformers import is_torch_available
 
 from .test_configuration_common import ConfigTester
@@ -357,6 +358,7 @@ class BartHeadTests(unittest.TestCase):
         loss = outputs[0]
         self.assertIsInstance(loss.item(), float)
 
+    @timeout_decorator.timeout(1)
     def test_lm_forward(self):
         config, input_ids, batch_size = self._get_config_and_data()
         lm_labels = ids_tensor([batch_size, input_ids.shape[1]], self.vocab_size).to(torch_device)