[Tests] Add combined pipeline tests (#4869)

* [Tests] Add combined pipeline tests

* Update tests/pipelines/kandinsky_v22/test_kandinsky.py

tests/pipelines/test_pipelines_combined.py

+# coding=utf-8
+# Copyright 2023 HuggingFace Inc.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import unittest
+
+import torch
+from huggingface_hub import ModelCard
+
+from diffusers import DiffusionPipeline, KandinskyV22CombinedPipeline, KandinskyV22Pipeline, KandinskyV22PriorPipeline
+from diffusers.pipelines.pipeline_utils import CONNECTED_PIPES_KEYS
+
+
+def state_dicts_almost_equal(sd1, sd2):
+    sd1 = dict(sorted(sd1.items()))
+    sd2 = dict(sorted(sd2.items()))
+
+    models_are_equal = True
+    for ten1, ten2 in zip(sd1.values(), sd2.values()):
+        if (ten1 - ten2).abs().sum() > 1e-3:
+            models_are_equal = False
+
+    return models_are_equal
+
+
+class CombinedPipelineFastTest(unittest.TestCase):
+    def modelcard_has_connected_pipeline(self, model_id):
+        modelcard = ModelCard.load(model_id)
+        connected_pipes = {prefix: getattr(modelcard.data, prefix, [None])[0] for prefix in CONNECTED_PIPES_KEYS}
+        connected_pipes = {k: v for k, v in connected_pipes.items() if v is not None}
+
+        return len(connected_pipes) > 0
+
+    def test_correct_modelcard_format(self):
+        # hf-internal-testing/tiny-random-kandinsky-v22-prior has no metadata
+        assert not self.modelcard_has_connected_pipeline("hf-internal-testing/tiny-random-kandinsky-v22-prior")
+
+        # see https://huggingface.co/hf-internal-testing/tiny-random-kandinsky-v22-decoder/blob/8baff9897c6be017013e21b5c562e5a381646c7e/README.md?code=true#L2
+        assert self.modelcard_has_connected_pipeline("hf-internal-testing/tiny-random-kandinsky-v22-decoder")
+
+    def test_load_connected_checkpoint_when_specified(self):
+        pipeline_prior = DiffusionPipeline.from_pretrained("hf-internal-testing/tiny-random-kandinsky-v22-prior")
+        pipeline_prior_connected = DiffusionPipeline.from_pretrained(
+            "hf-internal-testing/tiny-random-kandinsky-v22-prior", load_connected_pipeline=True
+        )
+
+        # Passing `load_connected_pipeline` to prior is a no-op as the pipeline has no connected pipeline
+        assert pipeline_prior.__class__ == pipeline_prior_connected.__class__
+
+        pipeline = DiffusionPipeline.from_pretrained("hf-internal-testing/tiny-random-kandinsky-v22-decoder")
+        pipeline_connected = DiffusionPipeline.from_pretrained(
+            "hf-internal-testing/tiny-random-kandinsky-v22-decoder", load_connected_pipeline=True
+        )
+
+        # Passing `load_connected_pipeline` to decoder loads the combined pipeline
+        assert pipeline.__class__ != pipeline_connected.__class__
+        assert pipeline.__class__ == KandinskyV22Pipeline
+        assert pipeline_connected.__class__ == KandinskyV22CombinedPipeline
+
+        # check that loaded components match prior and decoder components
+        assert set(pipeline_connected.components.keys()) == set(
+            ["prior_" + k for k in pipeline_prior.components.keys()] + list(pipeline.components.keys())
+        )
+
+    def test_load_connected_checkpoint_default(self):
+        prior = KandinskyV22PriorPipeline.from_pretrained("hf-internal-testing/tiny-random-kandinsky-v22-prior")
+        decoder = KandinskyV22Pipeline.from_pretrained("hf-internal-testing/tiny-random-kandinsky-v22-decoder")
+
+        # check that combined pipeline loads both prior & decoder because of
+        # https://huggingface.co/hf-internal-testing/tiny-random-kandinsky-v22-decoder/blob/8baff9897c6be017013e21b5c562e5a381646c7e/README.md?code=true#L3
+        assert (
+            KandinskyV22CombinedPipeline._load_connected_pipes
+        )  # combined pipelines will download more checkpoints that just the one specified
+        pipeline = KandinskyV22CombinedPipeline.from_pretrained(
+            "hf-internal-testing/tiny-random-kandinsky-v22-decoder"
+        )
+
+        prior_comps = prior.components
+        decoder_comps = decoder.components
+        for k, component in pipeline.components.items():
+            if k.startswith("prior_"):
+                k = k[6:]
+                comp = prior_comps[k]
+            else:
+                comp = decoder_comps[k]
+
+            if isinstance(component, torch.nn.Module):
+                assert state_dicts_almost_equal(component.state_dict(), comp.state_dict())
+            elif hasattr(component, "config"):
+                assert dict(component.config) == dict(comp.config)
+            else:
+                assert component.__class__ == comp.__class__