use assert[Not]In where appropriate
diff --git a/Lib/test/test_bytes.py b/Lib/test/test_bytes.py
index 666894f..a72e8de 100644
--- a/Lib/test/test_bytes.py
+++ b/Lib/test/test_bytes.py
@@ -222,27 +222,26 @@
 
     def test_contains(self):
         b = self.type2test(b"abc")
-        self.assertTrue(ord('a') in b)
-        self.assertTrue(int(ord('a')) in b)
-        self.assertFalse(200 in b)
-        self.assertFalse(200 in b)
+        self.assertIn(ord('a'), b)
+        self.assertIn(int(ord('a')), b)
+        self.assertNotIn(200, b)
         self.assertRaises(ValueError, lambda: 300 in b)
         self.assertRaises(ValueError, lambda: -1 in b)
         self.assertRaises(TypeError, lambda: None in b)
         self.assertRaises(TypeError, lambda: float(ord('a')) in b)
         self.assertRaises(TypeError, lambda: u"a" in b)
         for f in bytes, bytearray:
-            self.assertTrue(f(b"") in b)
-            self.assertTrue(f(b"a") in b)
-            self.assertTrue(f(b"b") in b)
-            self.assertTrue(f(b"c") in b)
-            self.assertTrue(f(b"ab") in b)
-            self.assertTrue(f(b"bc") in b)
-            self.assertTrue(f(b"abc") in b)
-            self.assertFalse(f(b"ac") in b)
-            self.assertFalse(f(b"d") in b)
-            self.assertFalse(f(b"dab") in b)
-            self.assertFalse(f(b"abd") in b)
+            self.assertIn(f(b""), b)
+            self.assertIn(f(b"a"), b)
+            self.assertIn(f(b"b"), b)
+            self.assertIn(f(b"c"), b)
+            self.assertIn(f(b"ab"), b)
+            self.assertIn(f(b"bc"), b)
+            self.assertIn(f(b"abc"), b)
+            self.assertNotIn(f(b"ac"), b)
+            self.assertNotIn(f(b"d"), b)
+            self.assertNotIn(f(b"dab"), b)
+            self.assertNotIn(f(b"abd"), b)
 
     def test_fromhex(self):
         self.assertRaises(TypeError, self.type2test.fromhex)