code: def test_substitute_single_word(self):
      texts = ["Zoology", "roku123456"]
      aug = RandomCharAug(action="substitute", min_char=1)
      for text in texts:
          augmented_data = aug.augment(text)
          augmented_text = augmented_data[0]
          self.assertNotEqual(text, augmented_text)
  
      self.assertTrue(len(texts) > 0)
  
file_path: nlpaug/test/augmenter/char/test_random_char.py
imports: import unittest
  from nlpaug.augmenter.char.random import RandomCharAug
label_desc: Use image node_id 3 for calling the TestRandomCharReplaceAug obj's underlying member method code with example usage: obj.test_substitute_single_word() without return types