Simplify HIDE_* env var test; add missing cases

Now that the expected truth values are intuitive, it is no longer
necessary to group them by result and include messages that
acknowldge the unintuitive cases. This reorders them so that pairs
(like "yes" and "no") appear together, removes the messages that
are no longer necessary, and reduces test code duplication.

This also adds cases to test leading/trailing whitespace in
otherwise nonempty strings, so it is clearer what the test is
asserting overall, and so a bug where lstrip or rstrip (or
equivalent with a regex) were used instead strip would be caught.

test/test_util.py

@@ -520,30 +520,22 @@ def run_parse(value):
             )
             return ast.literal_eval(output)
 
-        true_iff_win = os.name == "nt"  # Same as is_win, but don't depend on that here.
-
-        truthy_cases = [
-            ("unset", None),
-            ("true-seeming", "1"),
-            ("true-seeming", "true"),
-            ("true-seeming", "True"),
-            ("true-seeming", "yes"),
-            ("true-seeming", "YES"),
-        ]
-        falsy_cases = [
-            ("empty", ""),
-            ("whitespace", " "),
-            ("false-seeming", "0"),
-            ("false-seeming", "false"),
-            ("false-seeming", "False"),
-            ("false-seeming", "no"),
-            ("false-seeming", "NO"),
-        ]
-
-        for msg, env_var_value in truthy_cases:
-            with self.subTest(msg, env_var_value=env_var_value):
-                self.assertIs(run_parse(env_var_value), true_iff_win)
-
-        for msg, env_var_value in falsy_cases:
-            with self.subTest(msg, env_var_value=env_var_value):
-                self.assertIs(run_parse(env_var_value), False)
+        for env_var_value, expected_truth_value in (
+            (None, os.name == "nt"),  # True on Windows when the environment variable is unset.
+            ("", False),
+            (" ", False),
+            ("0", False),
+            ("1", os.name == "nt"),
+            ("false", False),
+            ("true", os.name == "nt"),
+            ("False", False),
+            ("True", os.name == "nt"),
+            ("no", False),
+            ("yes", os.name == "nt"),
+            ("NO", False),
+            ("YES", os.name == "nt"),
+            (" no  ", False),
+            (" yes  ", os.name == "nt"),
+        ):
+            with self.subTest(env_var_value=env_var_value):
+                self.assertIs(run_parse(env_var_value), expected_truth_value)