add tests to test Cell exceptions

cell.py

@@ -29,7 +29,7 @@ class Cell:
     TOP_WALL = 0
     BOTTOM_WALL = 1
     LEFT_WALL = 2
-    RIGHT_WALL = 4
+    RIGHT_WALL = 3
 
     def __init__(
             self,

tests.py

@@ -1,6 +1,7 @@
 import unittest
-from maze import Maze
+import cell
 from cell import Cell
+from maze import Maze
 
 
 class Tests(unittest.TestCase):
@@ -57,7 +58,48 @@ class Tests(unittest.TestCase):
             2,
         )
         self.assertFalse(maze._cells[0][0].wall_exists(Cell.TOP_WALL))
-        self.assertFalse(maze._cells[number_of_cell_rows - 1][number_of_cells_per_row - 1].wall_exists(Cell.BOTTOM_WALL))
+        self.assertFalse(
+            maze._cells[number_of_cell_rows - 1]
+            [number_of_cells_per_row - 1].wall_exists(Cell.BOTTOM_WALL)
+        )
+
+    def test_invalid_cell_exception(self):
+        """
+        test_invalid_cell_exception tests the exception for when an attempt
+        is made to create an invalid Cell.
+        """
+        cases = [
+            {"x1": 30, "y1": 50, "x2": 20, "y2": 100},
+            {"x1": 30, "y1": 50, "x2": 40, "y2": 25},
+        ]
+
+        for case in cases:
+            with self.assertRaises(cell.CellInvalidError):
+                _ = Cell(
+                    x1=case["x1"],
+                    y1=case["y1"],
+                    x2=case["x2"],
+                    y2=case["y2"]
+                )
+
+    def test_cell_too_small_exception(self):
+        """
+        test_cell_too_small_exception tests the excpetion for when an attempt
+        is made to create a Cell that's too small.
+        """
+        cases = [
+            {"x1": 1, "y1": 50, "x2": 2, "y2": 100},
+            {"x1": 30, "y1": 25, "x2": 40, "y2": 25},
+        ]
+
+        for case in cases:
+            with self.assertRaises(cell.CellTooSmallError):
+                _ = Cell(
+                    x1=case["x1"],
+                    y1=case["y1"],
+                    x2=case["x2"],
+                    y2=case["y2"]
+                )
 
 
 if __name__ == "__main__":