Better test for Issue #15402: Add a __sizeof__ method to struct.Struct

Doc/ACKS.txt

@@ -204,6 +204,7 @@ docs@python.org), and we'll be glad to correct the problem.
    * Anthony Starks
    * Greg Stein
    * Peter Stoehr
+   * Serhiy Storchaka
    * Mark Summerfield
    * Reuben Sumner
    * Kalle Svensson

Lib/test/test_struct.py

@@ -559,12 +559,12 @@ class StructTest(unittest.TestCase):
     def test_sizeof(self):
         self.assertGreater(sys.getsizeof(struct.Struct('BHILfdspP')),
                            sys.getsizeof(struct.Struct('B')))
-        self.assertGreaterEqual(sys.getsizeof(struct.Struct('123B')),
+        self.assertGreater(sys.getsizeof(struct.Struct('123B')),
                                 sys.getsizeof(struct.Struct('B')))
-        self.assertGreaterEqual(sys.getsizeof(struct.Struct('B' * 123)),
+        self.assertGreater(sys.getsizeof(struct.Struct('B' * 1234)),
+                                sys.getsizeof(struct.Struct('123B')))
+        self.assertGreater(sys.getsizeof(struct.Struct('1234B')),
                                 sys.getsizeof(struct.Struct('123B')))
-        self.assertGreaterEqual(sys.getsizeof(struct.Struct('123xB')),
-                                sys.getsizeof(struct.Struct('B')))
 
 def test_main():
     run_unittest(StructTest)