Improved testing
Adding some tests for some models that were not tested.
# [Codecov](https://codecov.io/gh/huggingface/transformers/pull/2723?src=pr&el=h1) Report
> Merging [#2723](https://codecov.io/gh/huggingface/transformers/pull/2723?src=pr&el=desc) into [master](https://codecov.io/gh/huggingface/transformers/commit/6c1b23554f8bb5b5e1f6c80969acab764c755678?src=pr&el=desc) will **increase** coverage by `0.93%`.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/huggingface/transformers/pull/2723/graphs/tree.svg?width=650&token=9qOlN6Hb1c&height=150&src=pr)](https://codecov.io/gh/huggingface/transformers/pull/2723?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master    #2723      +/-   ##
==========================================
+ Coverage   74.09%   75.03%   +0.93%     
==========================================
  Files          93       93              
  Lines       15248    15248              
==========================================
+ Hits        11298    11441     +143     
+ Misses       3950     3807     -143
```


| [Impacted Files](https://codecov.io/gh/huggingface/transformers/pull/2723?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [src/transformers/configuration\_flaubert.py](https://codecov.io/gh/huggingface/transformers/pull/2723/diff?src=pr&el=tree#diff-c3JjL3RyYW5zZm9ybWVycy9jb25maWd1cmF0aW9uX2ZsYXViZXJ0LnB5) | `100% <0%> (+25%)` | :arrow_up: |
| [src/transformers/modeling\_roberta.py](https://codecov.io/gh/huggingface/transformers/pull/2723/diff?src=pr&el=tree#diff-c3JjL3RyYW5zZm9ybWVycy9tb2RlbGluZ19yb2JlcnRhLnB5) | `95.77% <0%> (+30.51%)` | :arrow_up: |
| [src/transformers/modeling\_flaubert.py](https://codecov.io/gh/huggingface/transformers/pull/2723/diff?src=pr&el=tree#diff-c3JjL3RyYW5zZm9ybWVycy9tb2RlbGluZ19mbGF1YmVydC5weQ==) | `83.82% <0%> (+55.14%)` | :arrow_up: |

------

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> Powered by [Codecov](https://codecov.io/gh/huggingface/transformers/pull/2723?src=pr&el=footer). Last update [6c1b235...74b1cb3](https://codecov.io/gh/huggingface/transformers/pull/2723?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
