Fix solved property

sudoku.py

@@ -91,12 +91,9 @@ class Sudoku:
 
     @property
     def solved(self):
-        expected = set(range(self.size))
-        return all([
-            all(expected == set(row) for row in self.rows),
-            all(expected == set(col) for col in self.columns),
-            all(expected == set(sqr) for sqr in self.squares)
-        ])
+        expected = set(range(1, self.size + 1))
+        all_groups = itertools.chain(self.rows, self.columns, self.squares)
+        return all(expected == set(g) for g in all_groups)
 
     def _apply_index_ranges(self, ranges):
         return ((self._board[i] for i in r) for r in ranges)

test.py

@@ -83,3 +83,8 @@ class Sudoku4BasicTests(Sudoku4TestCase):
 class Sudoku4SolvedTests(Sudoku4TestCase):
     def test_that_an_empty_board_is_not_solved(self):
         self.assertFalse(self.board.solved)
+
+    def test_simple_solution_is_solved(self):
+        board = (int(i) for i in '1234341221434321')
+        self.board = sudoku.Sudoku(4, board)
+        self.assertTrue(self.board.solved)