use assert[Not]In where appropriate
diff --git a/Lib/test/test_subprocess.py b/Lib/test/test_subprocess.py
index 1693c6b..db93393 100644
--- a/Lib/test/test_subprocess.py
+++ b/Lib/test/test_subprocess.py
@@ -76,7 +76,7 @@
         # check_output() function with zero return code
         output = subprocess.check_output(
                 [sys.executable, "-c", "print 'BDFL'"])
-        self.assertTrue('BDFL' in output)
+        self.assertIn('BDFL', output)
 
     def test_check_output_nonzero(self):
         # check_call() function with non-zero return code
@@ -93,7 +93,7 @@
         output = subprocess.check_output(
                 [sys.executable, "-c", "import sys; sys.stderr.write('BDFL')"],
                 stderr=subprocess.STDOUT)
-        self.assertTrue('BDFL' in output)
+        self.assertIn('BDFL', output)
 
     def test_check_output_stdout_arg(self):
         # check_output() function stderr redirected to stdout
@@ -102,7 +102,7 @@
                     [sys.executable, "-c", "print 'will not be run'"],
                     stdout=sys.stdout)
         except ValueError, e:
-            self.assertTrue('stdout' in e.args[0])
+            self.assertIn('stdout', e.args[0])
         else:
             self.fail("Expected ValueError when stdout arg supplied.")