Tests: move generate tests to the right mixin and delete redundant tests (#34464)

* tmp commit

* tmp commit

* cull overwrites of deleted tests

* typo

* more specific docstring

* make fixup

* parameterize at the top?

* correction

* more deletions :D

* tmp commit

* for VLMs too

* fix _check_outputs

* test nit

* make fixup

* fix another flaky

* test_generate_from_inputs_embeds -- handle missing attention mask

tests/models/mamba2/test_modeling_mamba2.py

@@ -204,8 +204,8 @@ class Mamba2ModelTest(ModelTesterMixin, GenerationTesterMixin, PipelineTesterMix
         pass
 
     @unittest.skip(reason="To fix, Mamba 2 cache slicing test case is an edge case")
-    @parameterized.expand([(1,), (2,)])
-    def test_generate_from_inputs_embeds_decoder_only(self, num_beams):
+    @parameterized.expand([("greedy", 1), ("beam search", 2)])
+    def test_generate_from_inputs_embeds(self, _, num_beams):
         pass
 
     @unittest.skip(reason="To fix, Mamba 2 cache slicing test case is an edge case")
@@ -276,12 +276,6 @@ class Mamba2ModelTest(ModelTesterMixin, GenerationTesterMixin, PipelineTesterMix
             dict_inputs = self._prepare_for_class(inputs_dict, model_class, return_labels=True)
             check_equivalence(model, tuple_inputs, dict_inputs, {"output_hidden_states": True})
 
-    @unittest.skip(
-        reason="Mamba2 does not support generating with input embeddings (custom cache_position computation)"
-    )
-    def test_inputs_embeds_matches_input_ids_with_generate(self):
-        pass
-
 
 @require_torch
 @slow