code: def test_single_column_factorize_columns():
      """Tests if Single Column Factorize is working correctly"""
      df = pd.DataFrame(
          {"a": ["hello", "hello", "sup"], "b": [1, 2, 3]}
      ).factorize_columns(column_names="a")
      assert "a_enc" in df.columns
  
file_path: pyjanitor/tests/functions/test_factorize_columns.py
imports: import pandas
  import pytest
  import janitor
label_desc: Use image node_id 1 for calling a global function with example usage: test_single_column_factorize_columns() without return types