Improve tests.

Author: serhiy-storchaka

Lib/test/test_socket.py

@@ -1225,27 +1225,22 @@ def testNtoH(self):
             self.assertEqual(swapped & mask, mask)
             self.assertRaises(OverflowError, func, 1<<34)
 
-    @support.cpython_only
-    @unittest.skipIf(_testcapi is None, "requires _testcapi")
     def testNtoHErrors(self):
-        import _testcapi
         s_good_values = [0, 1, 2, 0xffff]
         l_good_values = s_good_values + [0xffffffff]
+        neg_values = [-1, -2, -(1<<15)-1, -(1<<31)-1, -(1<<63)-1, -1<<1000]
         l_bad_values = [1<<32, 1<<1000]
-        s_bad_values = (
-            l_bad_values +
-            [1 << 16, _testcapi.INT_MAX, _testcapi.INT_MAX+1]
-        )
+        s_bad_values = l_bad_values + [1 << 16, (1<<31)-1, 1<<31]
         for k in s_good_values:
             socket.ntohs(k)
             socket.htons(k)
         for k in l_good_values:
             socket.ntohl(k)
             socket.htonl(k)
-        for k in -1, -2, _testcapi.INT_MIN-1, -1<<1000:
+        for k in neg_values:
             self.assertRaises(ValueError, socket.ntohs, k)
-            self.assertRaises(ValueError, socket.ntohl, k)
             self.assertRaises(ValueError, socket.htons, k)
+            self.assertRaises(ValueError, socket.ntohl, k)
             self.assertRaises(ValueError, socket.htonl, k)
         for k in s_bad_values:
             self.assertRaises(OverflowError, socket.ntohs, k)