text: """Tests for the saddle-points exercise
  
  Implementation note:
  The saddle_points function must validate the input matrix and raise a
  ValueError with a meaningful error message if the matrix turns out to be
  irregular.
  """
  import unittest
  
  from saddle_points import saddle_points
  
  # Tests adapted from `problem-specifications//canonical-data.json` @ v1.5.0
  
  
  def sorted_points(point_list):
      return sorted(point_list, key=lambda p: (p["row"], p["column"]))
  
  
  class SaddlePointsTest(unittest.TestCase):
      def test_can_identify_single_saddle_point(self):
          matrix = [[9, 8, 7], [5, 3, 2], [6, 6, 7]]
          self.assertEqual(
              sorted_points(saddle_points(matrix)),
              sorted_points([{"row": 2, "column": 1}]),
          )
  
      def test_can_identify_that_empty_matrix_has_no_saddle_points(self):
          matrix = []
          self.assertEqual(sorted_points(saddle_points(matrix)), sorted_points([]))
  
      def test_can_identify_lack_of_saddle_points_when_there_are_none(self):
          matrix = [[1, 2, 3], [3, 1, 2], [2, 3, 1]]
          self.assertEqual(sorted_points(saddle_points(matrix)), sorted_points([]))
  
      def test_can_identify_multiple_saddle_points_in_a_column(self):
          matrix = [[4, 5, 4], [3, 5, 5], [1, 5, 4]]
          self.assertEqual(
              sorted_points(saddle_points(matrix)),
              sorted_points(
                  [
                      {"row": 1, "column": 2},
                      {"row": 2, "column": 2},
                      {"row": 3, "column": 2},
                  ]
              ),
          )
  
      def test_can_identify_multiple_saddle_points_in_a_row(self):
          matrix = [[6, 7, 8], [5, 5, 5], [7, 5, 6]]
          self.assertEqual(
              sorted_points(saddle_points(matrix)),
              sorted_points(
                  [
                      {"row": 2, "column": 1},
                      {"row": 2, "column": 2},
                      {"row": 2, "column": 3},
                  ]
              ),
          )
  
      def test_can_identify_saddle_point_in_bottom_right_corner(self):
          matrix = [[8, 7, 9], [6, 7, 6], [3, 2, 5]]
          self.assertEqual(
              sorted_points(saddle_points(matrix)),
              sorted_points([{"row": 3, "column": 3}]),
          )
  
      def test_can_identify_saddle_points_in_a_non_square_matrix(self):
          matrix = [[3, 1, 3], [3, 2, 4]]
          self.assertEqual(
              sorted_points(saddle_points(matrix)),
              sorted_points([{"row": 1, "column": 3}, {"row": 1, "column": 1}]),
          )
  
      def test_can_identify_that_saddle_points_in_a_single_column_matrix_are_those_with_the_minimum_value(
          self
      ):
          matrix = [[2], [1], [4], [1]]
          self.assertEqual(
              sorted_points(saddle_points(matrix)),
              sorted_points([{"row": 2, "column": 1}, {"row": 4, "column": 1}]),
          )
  
      def test_can_identify_that_saddle_points_in_a_single_row_matrix_are_those_with_the_maximum_value(
          self
      ):
          matrix = [[2, 5, 3, 5]]
          self.assertEqual(
              sorted_points(saddle_points(matrix)),
              sorted_points([{"row": 1, "column": 2}, {"row": 1, "column": 4}]),
          )
  
      # Additional tests for this track
  
      def test_irregular_matrix(self):
          matrix = [[3, 2, 1], [0, 1], [2, 1, 0]]
          with self.assertRaisesWithMessage(ValueError):
              saddle_points(matrix)
  
      # Utility functions
      def setUp(self):
          try:
              self.assertRaisesRegex
          except AttributeError:
              self.assertRaisesRegex = self.assertRaisesRegexp
  
      def assertRaisesWithMessage(self, exception):
          return self.assertRaisesRegex(exception, r".+")
  
  
  if __name__ == "__main__":
      unittest.main()
  