diff --git a/Lib/test/mailcap.txt b/Lib/test/mailcap.txt
new file mode 100644
index 00000000000..f61135d8e54
--- /dev/null
+++ b/Lib/test/mailcap.txt
@@ -0,0 +1,39 @@
+# Mailcap file for test_mailcap; based on RFC 1524
+# Referred to by test_mailcap.py
+
+#
+# This is a comment.
+#
+
+application/frame; showframe %s; print="cat %s | lp"
+application/postscript; ps-to-terminal %s;\
+    needsterminal
+application/postscript; ps-to-terminal %s; \
+    compose=idraw %s
+application/x-dvi; xdvi %s
+application/x-movie; movieplayer %s; compose=moviemaker %s; \
+       description="Movie"; \
+       x11-bitmap="/usr/lib/Zmail/bitmaps/movie.xbm"
+application/*; echo "This is \"%t\" but \
+       is 50 \% Greek to me" \; cat %s; copiousoutput
+
+audio/basic; showaudio %s; compose=audiocompose %s; edit=audiocompose %s;\
+description="An audio fragment"
+audio/* ; /usr/local/bin/showaudio %t
+
+image/rgb; display %s
+#image/gif; display %s
+image/x-xwindowdump; display %s
+
+# The continuation char shouldn't \
+# make a difference in a comment.
+
+message/external-body; showexternal %s %{access-type} %{name} %{site} \
+    %{directory} %{mode} %{server}; needsterminal; composetyped = extcompose %s; \
+    description="A reference to data stored in an external location"
+
+text/richtext; shownonascii iso-8859-8 -e richtext -p %s; test=test "`echo \
+    %{charset} | tr '[A-Z]' '[a-z]'`"  = iso-8859-8; copiousoutput
+
+video/mpeg; mpeg_play %s
+video/*; animate %s
diff --git a/Lib/test/test_mailcap.py b/Lib/test/test_mailcap.py
new file mode 100644
index 00000000000..77ca294306e
--- /dev/null
+++ b/Lib/test/test_mailcap.py
@@ -0,0 +1,203 @@
+import mailcap
+import os
+import shutil
+import test.support
+import unittest
+
+# Location of mailcap file
+MAILCAPFILE = test.support.findfile("mailcap.txt")
+
+# Dict to act as mock mailcap entry for this test
+# The keys and values should match the contents of MAILCAPFILE
+MAILCAPDICT = {'application/x-movie': [{'compose': 'moviemaker %s',
+                                        'x11-bitmap': '"/usr/lib/Zmail/bitmaps/movie.xbm"',
+                                        'description': '"Movie"',
+                                        'view': 'movieplayer %s'}],
+               'application/*': [{'copiousoutput': '',
+                                  'view': 'echo "This is \\"%t\\" but        is 50 \\% Greek to me" \\; cat %s'}],
+               'audio/basic': [{'edit': 'audiocompose %s',
+                                'compose': 'audiocompose %s',
+                                'description': '"An audio fragment"',
+                                'view': 'showaudio %s'}],
+               'video/mpeg': [{'view': 'mpeg_play %s'}],
+               'application/postscript': [{'needsterminal': '',
+                                           'view': 'ps-to-terminal %s'},
+                                          {'compose': 'idraw %s',
+                                           'view': 'ps-to-terminal %s'}],
+               'application/x-dvi': [{'view': 'xdvi %s'}],
+               'message/external-body': [{'composetyped': 'extcompose %s',
+                                          'description': '"A reference to data stored in an external location"',
+                                          'needsterminal': '',
+                                          'view': 'showexternal %s %{access-type} %{name} %{site}     %{directory} %{mode} %{server}'}],
+               'text/richtext': [{'test': 'test "`echo     %{charset} | tr \'[A-Z]\' \'[a-z]\'`"  = iso-8859-8',
+                                  'copiousoutput': '',
+                                  'view': 'shownonascii iso-8859-8 -e richtext -p %s'}],
+               'image/x-xwindowdump': [{'view': 'display %s'}],
+               'audio/*': [{'view': '/usr/local/bin/showaudio %t'}],
+               'video/*': [{'view': 'animate %s'}],
+               'application/frame': [{'print': '"cat %s | lp"',
+                                      'view': 'showframe %s'}],
+               'image/rgb': [{'view': 'display %s'}]}
+
+
+class HelperFunctionTest(unittest.TestCase):
+
+    def test_listmailcapfiles(self):
+        # The return value for listmailcapfiles() will vary by system.
+        # So verify that listmailcapfiles() returns a list of strings that is of
+        # non-zero length.
+        mcfiles = mailcap.listmailcapfiles()
+        self.assertTrue(isinstance(mcfiles, list))
+        self.assertTrue(all([isinstance(m, str) for m in mcfiles]))
+        with test.support.EnvironmentVarGuard() as env:
+            # According to RFC 1524, if MAILCAPS env variable exists, use that
+            # and only that.
+            if "MAILCAPS" in env:
+                env_mailcaps = env["MAILCAPS"].split(os.pathsep)
+            else:
+                env_mailcaps = ["/testdir1/.mailcap", "/testdir2/mailcap"]
+                env["MAILCAPS"] = os.pathsep.join(env_mailcaps)
+                mcfiles = mailcap.listmailcapfiles()
+        self.assertEqual(env_mailcaps, mcfiles)
+
+    def test_readmailcapfile(self):
+        # Test readmailcapfile() using test file. It should match MAILCAPDICT.
+        with open(MAILCAPFILE, 'r') as mcf:
+            d = mailcap.readmailcapfile(mcf)
+        self.assertDictEqual(d, MAILCAPDICT)
+
+    def test_lookup(self):
+        # Test without key
+        expected = [{'view': 'mpeg_play %s'}, {'view': 'animate %s'}]
+        actual = mailcap.lookup(MAILCAPDICT, 'video/mpeg')
+        self.assertListEqual(expected, actual)
+
+        # Test with key
+        key = 'compose'
+        expected = [{'edit': 'audiocompose %s',
+                     'compose': 'audiocompose %s',
+                     'description': '"An audio fragment"',
+                     'view': 'showaudio %s'}]
+        actual = mailcap.lookup(MAILCAPDICT, 'audio/basic', key)
+        self.assertListEqual(expected, actual)
+
+    def test_subst(self):
+        plist = ['id=1', 'number=2', 'total=3']
+        # test case: ([field, MIMEtype, filename, plist=[]], <expected string>)
+        test_cases = [
+                      (["", "audio/*", "foo.txt"], ""),
+                      (["echo foo", "audio/*", "foo.txt"], "echo foo"),
+                      (["echo %s", "audio/*", "foo.txt"], "echo foo.txt"),
+                      (["echo %t", "audio/*", "foo.txt"], "echo audio/*"),
+                      (["echo \%t", "audio/*", "foo.txt"], "echo %t"),
+                      (["echo foo", "audio/*", "foo.txt", plist], "echo foo"),
+                      (["echo %{total}", "audio/*", "foo.txt", plist], "echo 3")
+                      ]
+        for tc in test_cases:
+            self.assertEqual(mailcap.subst(*tc[0]), tc[1])
+
+
+class GetcapsTest(unittest.TestCase):
+
+    def test_mock_getcaps(self):
+        # Test mailcap.getcaps() using mock mailcap file in this dir.
+        # Temporarily override any existing system mailcap file by pointing the
+        # MAILCAPS environment variable to our mock file.
+        with test.support.EnvironmentVarGuard() as env:
+            env["MAILCAPS"] = MAILCAPFILE
+            caps = mailcap.getcaps()
+            self.assertDictEqual(caps, MAILCAPDICT)
+
+    def test_system_mailcap(self):
+        # Test mailcap.getcaps() with mailcap file(s) on system, if any.
+        caps = mailcap.getcaps()
+        self.assertTrue(isinstance(caps, dict))
+        mailcapfiles = mailcap.listmailcapfiles()
+        existingmcfiles = [mcf for mcf in mailcapfiles if os.path.exists(mcf)]
+        if existingmcfiles:
+            # At least 1 mailcap file exists, so test that.
+            for (k, v) in caps.items():
+                self.assertTrue(isinstance(k, str))
+                self.assertTrue(isinstance(v, list))
+                self.assertTrue(all([isinstance(e, dict) for e in v]))
+        else:
+            # No mailcap files on system. getcaps() should return empty dict.
+            self.assertEqual({}, caps)
+
+
+class FindmatchTest(unittest.TestCase):
+
+    def test_findmatch(self):
+
+        # default findmatch arguments
+        c = MAILCAPDICT
+        fname = "foo.txt"
+        plist = ["access-type=default", "name=john", "site=python.org",
+                 "directory=/tmp", "mode=foo", "server=bar"]
+        audio_basic_entry = {'edit': 'audiocompose %s',
+                             'compose': 'audiocompose %s',
+                             'description': '"An audio fragment"',
+                             'view': 'showaudio %s'}
+        audio_entry = {"view": "/usr/local/bin/showaudio %t"}
+        video_entry = {'view': 'animate %s'}
+        message_entry = {'composetyped': 'extcompose %s',
+                         'description': '"A reference to data stored in an external location"', 'needsterminal': '',
+                         'view': 'showexternal %s %{access-type} %{name} %{site}     %{directory} %{mode} %{server}'}
+
+        # test case: (findmatch args, findmatch keyword args, expected output)
+        #   positional args: caps, MIMEtype
+        #   keyword args: key="view", filename="/dev/null", plist=[]
+        #   output: (command line, mailcap entry)
+        cases = [
+            ([{}, "video/mpeg"], {}, (None, None)),
+            ([c, "foo/bar"], {}, (None, None)),
+            ([c, "video/mpeg"], {}, ('mpeg_play /dev/null', {'view': 'mpeg_play %s'})),
+            ([c, "audio/basic", "edit"], {}, ("audiocompose /dev/null", audio_basic_entry)),
+            ([c, "audio/basic", "compose"], {}, ("audiocompose /dev/null", audio_basic_entry)),
+            ([c, "audio/basic", "description"], {}, ('"An audio fragment"', audio_basic_entry)),
+            ([c, "audio/basic", "foobar"], {}, (None, None)),
+            ([c, "video/*"], {"filename": fname}, ("animate %s" % fname, video_entry)),
+            ([c, "audio/basic", "compose"],
+             {"filename": fname},
+             ("audiocompose %s" % fname, audio_basic_entry)),
+            ([c, "audio/basic"],
+             {"key": "description", "filename": fname},
+             ('"An audio fragment"', audio_basic_entry)),
+            ([c, "audio/*"],
+             {"filename": fname},
+             ("/usr/local/bin/showaudio audio/*", audio_entry)),
+            ([c, "message/external-body"],
+             {"plist": plist},
+             ("showexternal /dev/null default john python.org     /tmp foo bar", message_entry))
+            ]
+        self._run_cases(cases)
+
+    @unittest.skipUnless(os.name == "posix", "Requires 'test' command on system")
+    def test_test(self):
+        # findmatch() will automatically check any "test" conditions and skip
+        # the entry if the check fails.
+        caps = {"test/pass": [{"test": "test 1 -eq 1"}],
+                "test/fail": [{"test": "test 1 -eq 0"}]}
+        # test case: (findmatch args, findmatch keyword args, expected output)
+        #   positional args: caps, MIMEtype, key ("test")
+        #   keyword args: N/A
+        #   output: (command line, mailcap entry)
+        cases = [
+            # findmatch will return the mailcap entry for test/pass because it evaluates to true
+            ([caps, "test/pass", "test"], {}, ("test 1 -eq 1", {"test": "test 1 -eq 1"})),
+            # findmatch will return None because test/fail evaluates to false
+            ([caps, "test/fail", "test"], {}, (None, None))
+            ]
+        self._run_cases(cases)
+
+    def _run_cases(self, cases):
+        for c in cases:
+            self.assertEqual(mailcap.findmatch(*c[0], **c[1]), c[2])
+
+
+def test_main():
+    test.support.run_unittest(HelperFunctionTest, GetcapsTest, FindmatchTest)
+
+
+if __name__ == '__main__':
+    test_main()
diff --git a/Misc/NEWS b/Misc/NEWS
index 67e8218013e..ab70dfd8679 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -1209,6 +1209,8 @@ Extension Modules
 Tests
 -----
 
+- Issue #6484: Add unit tests for mailcap module (patch by Gregory Nofi)
+
 - Issue #11651: Improve the Makefile test targets to run more of the test suite
   more quickly. The --multiprocess option is now enabled by default, reducing
   the amount of time needed to run the tests. "make test" and "make quicktest"