Added instruction append on error handling and edited JinJa2 template and example.py. Regenerated test file.

Author: BethanyG

exercises/practice/go-counting/.docs/instructions.append.md

@@ -0,0 +1,14 @@
+# Instructions append
+
+## Exception messages
+
+Sometimes it is necessary to [raise an exception](https://docs.python.org/3/tutorial/errors.html#raising-exceptions). When you do this, you should always include a **meaningful error message** to indicate what the source of the error is. This makes your code more readable and helps significantly with debugging. For situations where you know that the error source will be a certain type, you can choose to raise one of the [built in error types](https://docs.python.org/3/library/exceptions.html#base-classes), but should still include a meaningful message.
+
+This particular exercise requires that you use the [raise statement](https://docs.python.org/3/reference/simple_stmts.html#the-raise-statement) to "throw" a `ValueError` when given invalid coordinates. The tests will only pass if you both `raise` the `exception` and include a message with it.
+
+To raise a `ValueError` with a message, write the message as an argument to the `exception` type:
+
+```python
+# when the coordinates for the piece are invalid
+raise ValueError('Invalid coordinate')
+```

exercises/practice/go-counting/.meta/example.py

@@ -37,7 +37,7 @@ def walk(self, x, y,
 
     def territory(self, x, y):
         if not self.valid(x, y):
-            raise ValueError('invalid coordinate')
+            raise ValueError('Invalid coordinate')
         if self.board[y][x] in STONES:
             return (NONE, set())
 

exercises/practice/go-counting/.meta/template.j2

@@ -15,11 +15,15 @@
 
 
 {% macro test_case(case) -%}
+    {%- set expected = case["expected"] %}
+    {%- set exp_error = expected["error"] %}
     def test_{{ case["description"] | to_snake }}(self):
         board = Board({{ case["input"]["board"] }})
         {%- if case is error_case %}
-        with self.assertRaisesWithMessage(ValueError):
+        with self.assertRaises(ValueError) as err:
             board.territory(x={{ case["input"]["x"] }}, y={{ case["input"]["y"] }})
+        self.assertEqual(type(err.exception), ValueError)
+        self.assertEqual(err.exception.args[0], "{{ exp_error }}")
         {%- else %}
         {%- if "owner" in case["expected"] %}
         stone, territory = board.territory(x={{ case["input"]["x"] }}, y={{ case["input"]["y"] }})

exercises/practice/go-counting/go_counting_test.py

@@ -37,23 +37,31 @@ def test_a_stone_and_not_a_territory_on_5x5_board(self):
 
     def test_invalid_because_x_is_too_low_for_5x5_board(self):
         board = Board(["  B  ", " B B ", "B W B", " W W ", "  W  "])
-        with self.assertRaisesWithMessage(ValueError):
+        with self.assertRaises(ValueError) as err:
             board.territory(x=-1, y=1)
+        self.assertEqual(type(err.exception), ValueError)
+        self.assertEqual(err.exception.args[0], "Invalid coordinate")
 
     def test_invalid_because_x_is_too_high_for_5x5_board(self):
         board = Board(["  B  ", " B B ", "B W B", " W W ", "  W  "])
-        with self.assertRaisesWithMessage(ValueError):
+        with self.assertRaises(ValueError) as err:
             board.territory(x=5, y=1)
+        self.assertEqual(type(err.exception), ValueError)
+        self.assertEqual(err.exception.args[0], "Invalid coordinate")
 
     def test_invalid_because_y_is_too_low_for_5x5_board(self):
         board = Board(["  B  ", " B B ", "B W B", " W W ", "  W  "])
-        with self.assertRaisesWithMessage(ValueError):
+        with self.assertRaises(ValueError) as err:
             board.territory(x=1, y=-1)
+        self.assertEqual(type(err.exception), ValueError)
+        self.assertEqual(err.exception.args[0], "Invalid coordinate")
 
     def test_invalid_because_y_is_too_high_for_5x5_board(self):
         board = Board(["  B  ", " B B ", "B W B", " W W ", "  W  "])
-        with self.assertRaisesWithMessage(ValueError):
+        with self.assertRaises(ValueError) as err:
             board.territory(x=1, y=5)
+        self.assertEqual(type(err.exception), ValueError)
+        self.assertEqual(err.exception.args[0], "Invalid coordinate")
 
     def test_one_territory_is_the_whole_board(self):
         board = Board([" "])
@@ -75,11 +83,3 @@ def test_two_region_rectangular_board(self):
         self.assertSetEqual(territories[BLACK], {(0, 0), (2, 0)})
         self.assertSetEqual(territories[WHITE], set())
         self.assertSetEqual(territories[NONE], set())
-
-    # Utility functions
-    def assertRaisesWithMessage(self, exception):
-        return self.assertRaisesRegex(exception, r".+")
-
-
-if __name__ == "__main__":
-    unittest.main()