[No merge] TF integration testing (#7621)

* stash

* TF Integration testing for ELECTRA, BERT, Longformer

* Trigger slow tests

* Apply suggestions from code review

tests/test_modeling_tf_electra.py

@@ -248,3 +248,19 @@ class TFElectraModelTest(TFModelTesterMixin, unittest.TestCase):
         for model_name in ["google/electra-small-discriminator"]:
             model = TFElectraModel.from_pretrained(model_name)
             self.assertIsNotNone(model)
+
+
+class TFElectraModelIntegrationTest(unittest.TestCase):
+    @slow
+    def test_inference_masked_lm(self):
+        model = TFElectraForPreTraining.from_pretrained("lysandre/tiny-electra-random")
+        input_ids = tf.constant([[0, 1, 2, 3, 4, 5]])
+        output = model(input_ids)[0]
+
+        expected_shape = [1, 6]
+        self.assertEqual(output.shape, expected_shape)
+
+        print(output[:, :3])
+
+        expected_slice = tf.constant([[-0.24651965, 0.8835437, 1.823782]])
+        tf.debugging.assert_near(output[:, :3], expected_slice, atol=1e-4)