Improve test protocol for inputs_embeds in TF

cc @lysandrejik

transformers/tests/modeling_tf_common_test.py

@@ -426,10 +426,15 @@ class TFCommonTestCases:
                     try:
                         x = wte([input_ids], mode="embedding")
                     except:
-                        if hasattr(self.model_tester, "embedding_size"):
-                            x = tf.ones(input_ids.shape + [model.config.embedding_size], dtype=tf.dtypes.float32)
-                        else:
-                            x = tf.ones(input_ids.shape + [self.model_tester.hidden_size], dtype=tf.dtypes.float32)
+                        x = wte([input_ids, None, None, None], mode="embedding")
+                # ^^ In our TF models, the input_embeddings can take slightly different forms,
+                # so we try a few of them.
+                # We used to fall back to just synthetically creating a dummy tensor of ones:
+                #
+                # if hasattr(self.model_tester, "embedding_size"):
+                #     x = tf.ones(input_ids.shape + [self.model_tester.embedding_size], dtype=tf.dtypes.float32)
+                # else:
+                #     x = tf.ones(input_ids.shape + [self.model_tester.hidden_size], dtype=tf.dtypes.float32)
                 inputs_dict["inputs_embeds"] = x
                 outputs = model(inputs_dict)