Add tests to Trainer (#6605)

* Add tests to Trainer

* Test if removing long breaks everything

* Remove ugly hack

* Fix distributed test

* Use float for number of epochs

src/transformers/data/data_collator.py

@@ -62,7 +62,7 @@ def default_data_collator(features: List[InputDataClass]) -> Dict[str, torch.Ten
             if isinstance(v, torch.Tensor):
                 batch[k] = torch.stack([f[k] for f in features])
             else:
-                batch[k] = torch.tensor([f[k] for f in features], dtype=torch.long)
+                batch[k] = torch.tensor([f[k] for f in features])
 
     return batch