Test `skip_guidance_layers` in SD3 pipeline (#10102)

* Test `skip_guidance_layers` in pipelines

* Move to test_pipeline_stable_diffusion_3

tests/pipelines/stable_diffusion_3/test_pipeline_stable_diffusion_3.py

@@ -225,6 +225,39 @@ class StableDiffusion3PipelineFastTests(unittest.TestCase, PipelineTesterMixin):
             original_image_slice, image_slice_disabled, atol=1e-2, rtol=1e-2
         ), "Original outputs should match when fused QKV projections are disabled."
 
+    def test_skip_guidance_layers(self):
+        components = self.get_dummy_components()
+        pipe = self.pipeline_class(**components)
+        pipe = pipe.to(torch_device)
+        pipe.set_progress_bar_config(disable=None)
+
+        inputs = self.get_dummy_inputs(torch_device)
+
+        output_full = pipe(**inputs)[0]
+
+        inputs_with_skip = inputs.copy()
+        inputs_with_skip["skip_guidance_layers"] = [0]
+        output_skip = pipe(**inputs_with_skip)[0]
+
+        self.assertFalse(
+            np.allclose(output_full, output_skip, atol=1e-5), "Outputs should differ when layers are skipped"
+        )
+
+        self.assertEqual(output_full.shape, output_skip.shape, "Outputs should have the same shape")
+
+        inputs["num_images_per_prompt"] = 2
+        output_full = pipe(**inputs)[0]
+
+        inputs_with_skip = inputs.copy()
+        inputs_with_skip["skip_guidance_layers"] = [0]
+        output_skip = pipe(**inputs_with_skip)[0]
+
+        self.assertFalse(
+            np.allclose(output_full, output_skip, atol=1e-5), "Outputs should differ when layers are skipped"
+        )
+
+        self.assertEqual(output_full.shape, output_skip.shape, "Outputs should have the same shape")
+
 
 @slow
 @require_big_gpu_with_torch_cuda