docstr: Test if the component runs with a single document.
docstr_tok: ["Test","if","the","component","runs","with","a","single","document","."]
code: def test_run_single_document(self):
      """
      Test if the component runs with a single document.
      """
      ranker = TransformersSimilarityRanker(
          model="cross-encoder/ms-marco-MiniLM-L-6-v2", device=None
      )
      ranker.warm_up()
      docs_before = [Document(content="Berlin")]
      output = ranker.run(
          query="City in Germany", documents=docs_before
      )
      docs_after = output["documents"]
  
      assert len(docs_after) == 1
  
file_path: haystack/test/components/rankers/test_transformers_similarity.py
imports: from unittest.mock import MagicMock, patch
  import pytest
  import torch
  from transformers.modeling_outputs import SequenceClassifierOutput
  from haystack import Document, ComponentError
  from haystack.components.rankers.transformers_similarity import TransformersSimilarityRanker
label_desc: Use image node_id 12 for calling the TestSimilarityRanker obj's underlying member method code with example usage: obj.test_run_single_document() without return types