text: """Tests for the enumerate_on function."""
  from ampdup.util import enumerate_on
  
  
  def test_enumerate_empty_list():
      """Enumerate an empty list returns an empty iterable."""
      enumerated = enumerate_on(lambda x: True, [])
  
      assert list(enumerated) == []
  
  
  def test_enumerate_on_even_numbers():
      """Enumerate on a list of numbers, incrementing on even ones."""
      numbers = [1, 2, 3, 4, 5, 6, 7, 9, 11, 12]
  
      enumerated = enumerate_on(lambda x: x % 2 == 0, numbers)
  
      expected = [
          (0, 1),
          (1, 2),
          (1, 3),
          (2, 4),
          (2, 5),
          (3, 6),
          (3, 7),
          (3, 9),
          (3, 11),
          (4, 12),
      ]
  
      assert list(enumerated) == expected
  