old_contents: import engine
  
  
  VALID_COORDS = [(x, y) for x in xrange(97, 105) for y in xrange(49, 57)]
  INVALID_COORDS = [
      (0, 0), (-1, -1),
      (96, 49), (96, 48),
      (105, 49), (104, 48),
      (96, 56), (97, 57),
      (105, 56), (104, 57)
      ]
  VALID_A1 = [chr(x) + chr(y) for x in xrange(97, 105) for y in xrange(49, 57)]
  INVALID_A1 = ['a0', 'a9', 'h0', 'h9', 'z1', 'z8']
  
  
  def test_coord_to_a1():
      for coord in VALID_COORDS:
          assert engine._coord_to_a1.get(coord, False) is not False
      for coord in INVALID_COORDS:
          assert engine._coord_to_a1.get(coord, False) is False
  
  
  def test_a1_to_coord():
      for a1 in VALID_A1:
          assert engine._a1_to_coord.get(a1, False) is not False
      for a1 in INVALID_A1:
          assert engine._a1_to_coord.get(a1, False) is False
  
new_contents: import engine
  
  
  VALID_COORDS = [(x, y) for x in xrange(97, 105) for y in xrange(49, 57)]
  INVALID_COORDS = [
      (0, 0), (-1, -1),
      (96, 49), (96, 48),
      (105, 49), (104, 48),
      (96, 56), (97, 57),
      (105, 56), (104, 57)
      ]
  VALID_A1 = [chr(x) + chr(y) for x in xrange(97, 105) for y in xrange(49, 57)]
  INVALID_A1 = ['a0', 'a9', 'h0', 'h9', 'z1', 'z8']
  
  
  def test_coord_to_a1():
      for coord in VALID_COORDS:
          assert engine._coord_to_a1.get(coord, False) is not False
      for coord in INVALID_COORDS:
          assert engine._coord_to_a1.get(coord, False) is False
  
  
  def test_a1_to_coord():
      for a1 in VALID_A1:
          assert engine._a1_to_coord.get(a1, False) is not False
      for a1 in INVALID_A1:
          assert engine._a1_to_coord.get(a1, False) is False
  
  
  def test_is_coord_on_board():
      for coord in VALID_COORDS:
          assert engine._is_coord_on_board(coord) is True
      for coord in INVALID_COORDS:
          assert engine._is_coord_on_board(coord) is False
  
subject: Add test_is_coord_on_board() to assert the function returns True if the coordinate is on the board and False otherwise