bpo-31657: Add test coverage for the __debug__ case (GH-3450)

Update the compile tests for optimization levels to also check that
__debug__ blocks are included or excluded based on the optimization
level.
Patch by Diana Clarke.

Lib/test/test_builtin.py

@@ -328,19 +328,22 @@ class BuiltinTest(unittest.TestCase):
 
         codestr = '''def f():
         """doc"""
+        debug_enabled = False
+        if __debug__:
+            debug_enabled = True
         try:
             assert False
         except AssertionError:
-            return (True, f.__doc__)
+            return (True, f.__doc__, debug_enabled)
         else:
-            return (False, f.__doc__)
+            return (False, f.__doc__, debug_enabled)
         '''
         def f(): """doc"""
-        values = [(-1, __debug__, f.__doc__),
-                  (0, True, 'doc'),
-                  (1, False, 'doc'),
-                  (2, False, None)]
-        for optval, debugval, docstring in values:
+        values = [(-1, __debug__, f.__doc__, __debug__),
+                  (0, True, 'doc', True),
+                  (1, False, 'doc', False),
+                  (2, False, None, False)]
+        for optval, assertval, docstring, debugval in values:
             # test both direct compilation and compilation via AST
             codeobjs = []
             codeobjs.append(compile(codestr, "<test>", "exec", optimize=optval))
@@ -350,7 +353,7 @@ class BuiltinTest(unittest.TestCase):
                 ns = {}
                 exec(code, ns)
                 rv = ns['f']()
-                self.assertEqual(rv, (debugval, docstring))
+                self.assertEqual(rv, (assertval, docstring, debugval))
 
     def test_delattr(self):
         sys.spam = 1