Add test_peers(); fix up some errors found

sudoku.py

@@ -40,8 +40,7 @@ class Sudoku:
         '''
         Return an iterable of ranges of indexes into the board, each defining a row.
         '''
-        sz = self.size
-        return (self._row(i, size) for i in range(sz))
+        return (self._row(i, self.size) for i in range(self.size))
 
     @property
     def index_columns(self):
@@ -50,7 +49,7 @@ class Sudoku:
         '''
         sz = self.size
         sz2 = sz ** 2
-        return (self._column(c, sz, sz2) for i in range(sz))
+        return (self._column(i, sz, sz2) for i in range(sz))
 
     @property
     def index_squares(self):

test.py

@@ -14,7 +14,7 @@ class Sudoku4TestCase(unittest.TestCase):
 class Sudoku4BasicTests(Sudoku4TestCase):
     def test_that_board_is_sane(self):
         self.assertEqual(self.board.size, 4)
-        self.assertEqual(len(self.board.board), 4**2)
+        self.assertEqual(len(self.board._board), 4**2)
         self.assertEqual(self.board.dimension, 2)
 
     def test_rows(self):
@@ -53,6 +53,33 @@ class Sudoku4BasicTests(Sudoku4TestCase):
             with self.subTest(sq=sq_list, ex=exsq):
                 self.assertEqual(sq_list, exsq)
 
+    def test_peers(self):
+        expected_peers = {
+            (0,0): set([0, 1, 2, 3, 4, 8, 12, 5]),
+            (1,0): set([0, 1, 2, 3, 5, 9, 13, 4]),
+            (2,0): set([0, 1, 2, 3, 6, 10, 14, 7]),
+            (3,0): set([0, 1, 2, 3, 7, 11, 15, 6]),
+
+            (0,1): set([4, 5, 6, 7, 0, 8, 12, 1]),
+            (1,1): set([4, 5, 6, 7, 1, 9, 13, 0]),
+            (2,1): set([4, 5, 6, 7, 2, 10, 14, 3]),
+            (3,1): set([4, 5, 6, 7, 3, 11, 15, 2]),
+
+            (0,2): set([8, 9, 10, 11, 0, 4, 12, 13]),
+            (1,2): set([8, 9, 10, 11, 1, 5, 13, 12]),
+            (2,2): set([8, 9, 10, 11, 2, 6, 14, 15]),
+            (3,2): set([8, 9, 10, 11, 3, 7, 15, 14]),
+
+            (0,3): set([12, 13, 14, 15, 0, 4, 8, 9]),
+            (1,3): set([12, 13, 14, 15, 1, 5, 9, 8]),
+            (2,3): set([12, 13, 14, 15, 2, 6, 10, 11]),
+            (3,3): set([12, 13, 14, 15, 3, 7, 11, 10]),
+        }
+        for (coords, expeers) in expected_peers.items():
+            with self.subTest(coord=coords, ex=expeers):
+                peers = self.board.index_peers(*coords)
+                self.assertEqual(peers, expeers)
+
 class Sudoku4SolvedTests(Sudoku4TestCase):
     def test_that_an_empty_board_is_not_solved(self):
         self.assertFalse(self.board.solved)