[Tests] add requires peft decorator. (#11037)

* add requires peft decorator.

* install peft conditionally.

* conditional deps.
Co-authored-by: DN6 <dhruv.nair@gmail.com>

---------
Co-authored-by: DN6 <dhruv.nair@gmail.com>

.github/workflows/nightly_tests.yml

@@ -414,12 +414,16 @@ jobs:
         config:
           - backend: "bitsandbytes"
             test_location: "bnb"
+            additional_deps: ["peft"]
           - backend: "gguf"
             test_location: "gguf"
+            additional_deps: []
           - backend: "torchao"
             test_location: "torchao"
+            additional_deps: []
           - backend: "optimum_quanto"
             test_location: "quanto"
+            additional_deps: []
     runs-on:
       group: aws-g6e-xlarge-plus
     container:
@@ -437,6 +441,9 @@ jobs:
           python -m venv /opt/venv && export PATH="/opt/venv/bin:$PATH"
           python -m uv pip install -e [quality,test]
           python -m uv pip install -U ${{ matrix.config.backend }}
+          if [ "${{ join(matrix.config.additional_deps, ' ') }}" != "" ]; then
+              python -m uv pip install ${{ join(matrix.config.additional_deps, ' ') }}
+          fi
           python -m uv pip install pytest-reportlog
       - name: Environment
         run: |

tests/quantization/bnb/test_4bit.py

@@ -33,6 +33,7 @@ from diffusers.utils.testing_utils import (
     numpy_cosine_similarity_distance,
     require_accelerate,
     require_bitsandbytes_version_greater,
+    require_peft_backend,
     require_torch,
     require_torch_gpu,
     require_transformers_version_greater,
@@ -668,6 +669,7 @@ class SlowBnb4BitFluxTests(Base4bitTests):
         max_diff = numpy_cosine_similarity_distance(expected_slice, out_slice)
         self.assertTrue(max_diff < 1e-3)
 
+    @require_peft_backend
     def test_lora_loading(self):
         self.pipeline_4bit.load_lora_weights(
             hf_hub_download("ByteDance/Hyper-SD", "Hyper-FLUX.1-dev-8steps-lora.safetensors"), adapter_name="hyper-sd"