diff --git a/glymur/test/test_callbacks.py b/glymur/test/test_callbacks.py
index 2d4a3de..47ec100 100644
--- a/glymur/test/test_callbacks.py
+++ b/glymur/test/test_callbacks.py
@@ -6,16 +6,18 @@ import sys
 import tempfile
 import warnings
 
-if sys.hexversion < 0x03000000:
-    from StringIO import StringIO
-else:
-    from io import StringIO
-
 if sys.hexversion < 0x02070000:
     import unittest2 as unittest
 else:
     import unittest
 
+if sys.hexversion <= 0x03030000:
+    from mock import patch
+    from StringIO import StringIO
+else:
+    from unittest.mock import patch
+    from io import StringIO
+
 import glymur
 
 
@@ -24,15 +26,11 @@ import glymur
 class TestCallbacks(unittest.TestCase):
 
     def setUp(self):
-        # Save sys.stdout.
-        self.stdout = sys.stdout
-        sys.stdout = StringIO()
         self.jp2file = glymur.data.nemo()
         self.j2kfile = glymur.data.goodstuff()
 
     def tearDown(self):
-        # Restore stdout.
-        sys.stdout = self.stdout
+        pass
 
     @unittest.skipIf(os.name == "nt", "Temporary file issue on window.")
     def test_info_callback_on_write(self):
@@ -43,8 +41,9 @@ class TestCallbacks(unittest.TestCase):
             tiledata = j.read(tile=0)
         with tempfile.NamedTemporaryFile(suffix='.jp2') as tfile:
             j = glymur.Jp2k(tfile.name, 'wb')
-            j.write(tiledata, verbose=True)
-        actual = sys.stdout.getvalue().strip()
+            with patch('sys.stdout', new=StringIO()) as fake_out:
+                j.write(tiledata, verbose=True)
+                actual = fake_out.getvalue().strip()
         expected = '[INFO] tile number 1 / 1'
         self.assertEqual(actual, expected)
 
@@ -52,8 +51,9 @@ class TestCallbacks(unittest.TestCase):
         # Verify that we get the expected stdio output when our internal info
         # callback handler is enabled.
         j = glymur.Jp2k(self.j2kfile)
-        d = j.read(rlevel=1, verbose=True, area=(0, 0, 200, 150))
-        actual = sys.stdout.getvalue().strip()
+        with patch('sys.stdout', new=StringIO()) as fake_out:
+            d = j.read(rlevel=1, verbose=True, area=(0, 0, 200, 150))
+            actual = fake_out.getvalue().strip()
 
         lines = ['[INFO] Start to read j2k main header (0).',
                  '[INFO] Main header has been correctly decoded.',
@@ -72,47 +72,35 @@ class TestCallbacks15(unittest.TestCase):
     """This test suite is for OpenJPEG 1.5.1 properties.
     """
 
-    @classmethod
-    def setUpClass(cls):
-        # Monkey patch the package so as to use OPENJPEG instead of OPENJP2
-        cls.openjp2 = glymur.lib.openjp2.OPENJP2
-        glymur.lib.openjp2.OPENJP2 = None
-
-    @classmethod
-    def tearDownClass(cls):
-        # Restore OPENJP2
-        glymur.lib.openjp2.OPENJP2 = cls.openjp2
-
     def setUp(self):
-        # Save sys.stdout.
-        self.stdout = sys.stdout
-        sys.stdout = StringIO()
         self.jp2file = glymur.data.nemo()
         self.j2kfile = glymur.data.goodstuff()
 
     def tearDown(self):
-        # Restore stdout.
-        sys.stdout = self.stdout
+        pass
 
     def test_info_callbacks_on_read(self):
         # Verify that we get the expected stdio output when our internal info
         # callback handler is enabled.
-        j = glymur.Jp2k(self.j2kfile)
-        d = j.read(rlevel=1, verbose=True)
-        actual = sys.stdout.getvalue().strip()
-
-        regex = re.compile(r"""\[INFO\]\stile\s1\sof\s1\s+
-                               \[INFO\]\s-\stiers-1\stook\s
-                                       [0-9]+\.[0-9]+\ss\s+
-                               \[INFO\]\s-\sdwt\stook\s
-                                       (-){0,1}[0-9]+\.[0-9]+\ss\s+
-                               \[INFO\]\s-\stile\sdecoded\sin\s
-                                       [0-9]+\.[0-9]+\ss""",
-                           re.VERBOSE)
-        if sys.hexversion <= 0x03020000:
-            self.assertRegexpMatches(actual, regex)
-        else:
-            self.assertRegex(actual, regex)
+        with patch('glymur.lib.openjp2.OPENJP2', new=None):
+            # Force to use OPENJPEG instead of OPENJP2.
+            j = glymur.Jp2k(self.j2kfile)
+            with patch('sys.stdout', new=StringIO()) as fake_out:
+                d = j.read(rlevel=1, verbose=True)
+                actual = fake_out.getvalue().strip()
+    
+            regex = re.compile(r"""\[INFO\]\stile\s1\sof\s1\s+
+                                   \[INFO\]\s-\stiers-1\stook\s
+                                           [0-9]+\.[0-9]+\ss\s+
+                                   \[INFO\]\s-\sdwt\stook\s
+                                           (-){0,1}[0-9]+\.[0-9]+\ss\s+
+                                   \[INFO\]\s-\stile\sdecoded\sin\s
+                                           [0-9]+\.[0-9]+\ss""",
+                               re.VERBOSE)
+            if sys.hexversion <= 0x03020000:
+                self.assertRegexpMatches(actual, regex)
+            else:
+                self.assertRegex(actual, regex)
 
 
 if __name__ == "__main__":