Improve exception tests

README.md

@@ -22,6 +22,7 @@ A list of missing exercise can be found here: http://exercism.io/languages/pytho
 - We use minimalistic stub files for all exercises (#272).
 - We use `unittest` (Python Standard Library) and no 3rd-party-framework.
 - We use the parameter order `self.assertEqual(actual, expected)` (#440).
+- We use context managers (`with self.assertRaises(\<exception type\>):`) for testing for exceptions (#477).
 
 
 ### Testing

exercises/binary-search/binary_search_test.py

@@ -27,17 +27,20 @@ def test_finds_value_in_array_of_even_length(self):
             5)
 
     def test_identifies_value_missing(self):
-        self.assertRaises(ValueError, binary_search, [1, 3, 4, 6, 8, 9, 11], 7)
+        with self.assertRaises(ValueError):
+            binary_search([1, 3, 4, 6, 8, 9, 11], 7)
 
     def test_value_smaller_than_arrays_minimum(self):
-        self.assertRaises(ValueError, binary_search, [1, 3, 4, 6, 8, 9, 11], 0)
+        with self.assertRaises(ValueError):
+            binary_search([1, 3, 4, 6, 8, 9, 11], 0)
 
     def test_value_larger_than_arrays_maximum(self):
-        self.assertRaises(ValueError, binary_search, [1, 3, 4, 6, 8, 9, 11],
-                          13)
+        with self.assertRaises(ValueError):
+            binary_search([1, 3, 4, 6, 8, 9, 11], 13)
 
     def test_empty_array(self):
-        self.assertRaises(ValueError, binary_search, [], 1)
+        with self.assertRaises(ValueError):
+            binary_search([], 1)
 
 
 if __name__ == '__main__':

exercises/binary/binary_test.py

@@ -32,16 +32,20 @@ def test_binary_10001101000_is_decimal_1128(self):
         self.assertEqual(parse_binary("10001101000"), 1128)
 
     def test_invalid_binary_text_only(self):
-        self.assertRaises(ValueError, parse_binary, "carrot")
+        with self.assertRaises(ValueError):
+            parse_binary("carrot")
 
     def test_invalid_binary_number_not_base2(self):
-        self.assertRaises(ValueError, parse_binary, "102011")
+        with self.assertRaises(ValueError):
+            parse_binary("102011")
 
     def test_invalid_binary_numbers_with_text(self):
-        self.assertRaises(ValueError, parse_binary, "10nope")
+        with self.assertRaises(ValueError):
+            parse_binary("10nope")
 
     def test_invalid_binary_text_with_numbers(self):
-        self.assertRaises(ValueError, parse_binary, "nope10")
+        with self.assertRaises(ValueError):
+            parse_binary("nope10")
 
 
 if __name__ == '__main__':

exercises/meetup/meetup_test.py

@@ -399,8 +399,8 @@ def test_fifth_monday_of_march_2015(self):
             meetup_day(2015, 3, 'Monday', '5th'), date(2015, 3, 30))
 
     def test_nonexistent_fifth_monday_of_february_2015(self):
-        self.assertRaises(MeetupDayException, meetup_day, 2015, 2, 'Monday',
-                          '5th')
+        with self.assertRaises(MeetupDayException):
+            meetup_day(2015, 2, 'Monday', '5th')
 
 
 if __name__ == '__main__':

exercises/minesweeper/minesweeper_test.py

@@ -141,19 +141,22 @@ def test_different_len(self):
                "|*  |",
                "|  |",
                "+-+"]
-        self.assertRaises(ValueError, board, inp)
+        with self.assertRaises(ValueError):
+            board(inp)
 
     def test_faulty_border(self):
         inp = ["+-----+",
                "*   * |",
                "+-- --+"]
-        self.assertRaises(ValueError, board, inp)
+        with self.assertRaises(ValueError):
+            board(inp)
 
     def test_invalid_char(self):
         inp = ["+-----+",
                "|X  * |",
                "+-----+"]
-        self.assertRaises(ValueError, board, inp)
+        with self.assertRaises(ValueError):
+            board(inp)
 
 
 if __name__ == '__main__':

exercises/ocr-numbers/ocr_numbers_test.py

@@ -43,15 +43,17 @@ def test_unknown_char(self):
                                  "   "]), '?')
 
     def test_too_short_row(self):
-        self.assertRaises(ValueError, number, ["   ",
-                                               " _|",
-                                               " |",
-                                               "   "])
+        with self.assertRaises(ValueError):
+            number(["   ",
+                    " _|",
+                    " |",
+                    "   "])
 
     def test_insufficient_rows(self):
-        self.assertRaises(ValueError, number, ["   ",
-                                               " _|",
-                                               " X|"])
+        with self.assertRaises(ValueError):
+            number(["   ",
+                    " _|",
+                    " X|"])
 
     def test_grid0(self):
         self.assertEqual(grid('0'), [" _ ",
@@ -114,7 +116,8 @@ def test_grid3186547290(self):
             ])
 
     def test_invalid_grid(self):
-        self.assertRaises(ValueError, grid, '123a')
+        with self.assertRaises(ValueError):
+            grid('123a')
 
 
 if __name__ == '__main__':

exercises/pythagorean-triplet/pythagorean_triplet_test.py

@@ -80,7 +80,8 @@ def test_is_triplet3(self):
         self.assertIs(is_triplet((924, 43, 925)), True)
 
     def test_odd_number(self):
-        self.assertRaises(ValueError, primitive_triplets, 5)
+        with self.assertRaises(ValueError):
+            primitive_triplets(5)
 
 
 if __name__ == '__main__':

exercises/saddle-points/saddle_points_test.py

@@ -28,7 +28,8 @@ def test_empty_matrix(self):
 
     def test_irregular_matrix(self):
         inp = [[3, 2, 1], [0, 1], [2, 1, 0]]
-        self.assertRaises(ValueError, saddle_points, inp)
+        with self.assertRaises(ValueError):
+            saddle_points(inp)
 
 
 if __name__ == '__main__':

exercises/simple-cipher/simple_cipher_test.py

@@ -68,8 +68,10 @@ def test_cipher_random_key(self):
                         'All items in the key must be chars and lowercase!')
 
     def test_cipher_wrong_key(self):
-        self.assertRaises(ValueError, Cipher, 'a1cde')
-        self.assertRaises(ValueError, Cipher, 'aBcde')
+        with self.assertRaises(ValueError):
+            Cipher('a1cde')
+        with self.assertRaises(ValueError):
+            Cipher('aBcde')
 
 
 if __name__ == '__main__':

exercises/triangle/triangle_test.py

@@ -34,19 +34,24 @@ def test_very_small_triangles_are_legal(self):
         self.assertEqual(Triangle(0.4, 0.6, 0.3).kind(), "scalene")
 
     def test_triangles_with_no_size_are_illegal(self):
-        self.assertRaises(TriangleError, Triangle, 0, 0, 0)
+        with self.assertRaises(TriangleError):
+            Triangle(0, 0, 0)
 
     def test_triangles_with_negative_sides_are_illegal(self):
-        self.assertRaises(TriangleError, Triangle, 3, 4, -5)
+        with self.assertRaises(TriangleError):
+            Triangle(3, 4, -5)
 
     def test_triangles_violating_triangle_inequality_are_illegal(self):
-        self.assertRaises(TriangleError, Triangle, 1, 1, 3)
+        with self.assertRaises(TriangleError):
+            Triangle(1, 1, 3)
 
     def test_triangles_violating_triangle_inequality_are_illegal_2(self):
-        self.assertRaises(TriangleError, Triangle, 2, 4, 2)
+        with self.assertRaises(TriangleError):
+            Triangle(2, 4, 2)
 
     def test_triangles_violating_triangle_inequality_are_illegal_3(self):
-        self.assertRaises(TriangleError, Triangle, 7, 3, 2)
+        with self.assertRaises(TriangleError):
+            Triangle(7, 3, 2)
 
 
 if __name__ == '__main__':

exercises/wordy/wordy_test.py

@@ -49,17 +49,20 @@ def test_divide_twice(self):
             calculate("What is -12000 divided by 25 divided by -30?"), 16)
 
     def test_invalid_operation(self):
-        self.assertRaises(ValueError, calculate, "What is 4 xor 7?")
+        with self.assertRaises(ValueError):
+            calculate("What is 4 xor 7?")
 
     def test_missing_operation(self):
-        self.assertRaises(ValueError, calculate, "What is 2 2 minus 3?")
+        with self.assertRaises(ValueError):
+            calculate("What is 2 2 minus 3?")
 
     def test_missing_number(self):
-        self.assertRaises(ValueError, calculate,
-                          "What is 7 plus multiplied by -2?")
+        with self.assertRaises(ValueError):
+            calculate("What is 7 plus multiplied by -2?")
 
     def test_irrelevant_question(self):
-        self.assertRaises(ValueError, calculate, "Which is greater, 3 or 2?")
+        with self.assertRaises(ValueError):
+            calculate("Which is greater, 3 or 2?")
 
 
 if __name__ == '__main__':