text: from zigzag_conversion import Solution
  
  
  def test_example1():
      s = 'PAYPALISHIRING'
      num_rows = 3
      expected = 'PAHNAPLSIIGYIR'
  
      assert expected == Solution().convert(s, num_rows)
  
  
  def test_example2():
      s = 'PAYPALISHIRING'
      num_rows = 4
      expected = 'PINALSIGYAHRPI'
  
      assert expected == Solution().convert(s, num_rows)
  
  
  def test_example3():
      s = 'AB'
      num_rows = 1
      expected = 'AB'
  
      assert expected == Solution().convert(s, num_rows)
  