diff --git a/test/test_postprocessors.py b/test/test_postprocessors.py
index addb69d6f..5c2479722 100644
--- a/test/test_postprocessors.py
+++ b/test/test_postprocessors.py
@@ -1,4 +1,5 @@
 #!/usr/bin/env python
+# -*- coding: utf-8 -*-
 
 from __future__ import unicode_literals
 
@@ -9,9 +10,173 @@ import unittest
 sys.path.insert(0, os.path.dirname(os.path.dirname(os.path.abspath(__file__))))
 
 from youtube_dl.postprocessor import MetadataFromTitlePP
+from youtube_dl.postprocessor import XAttrMetadataPP
 
+from test.helper import (
+    FakeYDL
+)
 
 class TestMetadataFromTitle(unittest.TestCase):
     def test_format_to_regex(self):
         pp = MetadataFromTitlePP(None, '%(title)s - %(artist)s')
         self.assertEqual(pp._titleregex, '(?P<title>.+)\ \-\ (?P<artist>.+)')
+
+
+class TestXAttrMetadataPP(unittest.TestCase):
+    def test_run(self):
+        def sort_by_key(x):
+            return sorted(x, key=lambda x: x.get('key'))
+
+        pp = XAttrMetadataPP(None)
+        pp._downloader = FakeYDL()
+
+        written_xattrs = []
+        pp.write_xattr = lambda path, key, value: written_xattrs.append({'path': path, 'key': key, 'value': value})
+
+        # test empty raise exception
+        with self.assertRaises(KeyError) as context:
+            info = {}
+            pp.run(info)
+        self.assertEqual(written_xattrs, [])
+
+        # minimal test case
+        written_xattrs = []
+        info = {'filepath': 'foo'}
+        a, b = pp.run(info)
+        self.assertEqual(a, [])
+        self.assertEqual(b, info)
+        self.assertEqual(sort_by_key(written_xattrs), [
+            {'key': 'user.creator', 'path': 'foo', 'value': b'youtube-dl'},
+            {'key': 'user.dublincore.audience', 'path': 'foo', 'value': b'everybody'},
+            {'key': 'user.dublincore.type', 'path': 'foo', 'value': b'MovingImage'}
+        ])
+
+        # minimal test case with age limit >= 18
+        written_xattrs = []
+        info = {'filepath': 'foo', 'age_limit': 18}
+        a, b = pp.run(info)
+        self.assertEqual(a, [])
+        self.assertEqual(b, info)
+        self.assertEqual(sort_by_key(written_xattrs), [
+            {'key': 'user.creator', 'value': b'youtube-dl', 'path': 'foo'},
+            {'key': 'user.dublincore.audience', 'value': b'adults', 'path': 'foo'},
+            {'key': 'user.dublincore.type', 'value': b'MovingImage', 'path': 'foo'}
+        ])
+
+        # complete test-case
+        written_xattrs = []
+        info = {
+            'filepath': 'foo_filepath',
+            'age_limit': 19,
+            'webpage_url': 'foo_webpage',
+            'title': 'foo_title',
+            'upload_date': 'foo_upload_date',
+            'description': 'foo_description',
+            'uploader': 'foo_uploader',
+            'format': 'foo_format',
+            'tags': ['foo', 'bar'],
+            'categories':  ['FOO', 'baz', 'bar'],
+            'foo': 'this_should_be_ignored',
+        }
+        a, b = pp.run(info)
+        self.assertEqual(a, [])
+        self.assertEqual(b, info)
+        self.assertListEqual(sort_by_key(written_xattrs), [
+            {'key': 'user.creator', 'path': 'foo_filepath', 'value': b'youtube-dl'},
+            {'key': 'user.dublincore.audience', 'path': 'foo_filepath', 'value': b'adults'},
+            {'key': 'user.dublincore.contributor', 'path': 'foo_filepath', 'value': b'foo_uploader'},
+            {'key': 'user.dublincore.date', 'path': 'foo_filepath', 'value': b'foo_upload_date'},
+            {'key': 'user.dublincore.description', 'path': 'foo_filepath', 'value': b'foo_description'},
+            {'key': 'user.dublincore.format', 'path': 'foo_filepath', 'value': b'foo_format'},
+            {'key': 'user.dublincore.subject', 'path': 'foo_filepath', 'value': b'bar,baz,foo'},
+            {'key': 'user.dublincore.title', 'path': 'foo_filepath', 'value': b'foo_title'},
+            {'key': 'user.dublincore.type', 'path': 'foo_filepath', 'value': b'MovingImage'},
+            {'key': 'user.xdg.origin.url', 'path': 'foo_filepath', 'value': b'foo_webpage'},
+            {'key': 'user.xdg.referrer.url', 'path': 'foo_filepath', 'value': b'foo_webpage'},
+            {'key': 'user.xdg.tags', 'path': 'foo_filepath', 'value': b'bar,baz,foo'}
+        ])
+
+        # test-case with empty tags and categories
+        written_xattrs = []
+        info = {
+            'filepath': 'foo_filepath',
+            'age_limit': 19,
+            'webpage_url': 'foo_webpage',
+            'title': 'foo_title',
+            'upload_date': 'foo_upload_date',
+            'description': 'foo_description',
+            'uploader': 'foo_uploader',
+            'format': 'foo_format',
+            'tags': [],
+            'categories': None,
+            'foo': 'this_should_be_ignored',
+        }
+        a, b = pp.run(info)
+        self.assertEqual(a, [])
+        self.assertEqual(b, info)
+        self.assertEqual(sort_by_key(written_xattrs), [
+            {'path': 'foo_filepath', 'value': b'youtube-dl', 'key': 'user.creator'},
+            {'path': 'foo_filepath', 'value': b'adults', 'key': 'user.dublincore.audience'},
+            {'path': 'foo_filepath', 'value': b'foo_uploader', 'key': 'user.dublincore.contributor'},
+            {'path': 'foo_filepath', 'value': b'foo_upload_date', 'key': 'user.dublincore.date'},
+            {'path': 'foo_filepath', 'value': b'foo_description', 'key': 'user.dublincore.description'},
+            {'path': 'foo_filepath', 'value': b'foo_format', 'key': 'user.dublincore.format'},
+            {'path': 'foo_filepath', 'value': b'foo_title', 'key': 'user.dublincore.title'},
+            {'path': 'foo_filepath', 'value': b'MovingImage', 'key': 'user.dublincore.type'},
+            {'path': 'foo_filepath', 'value': b'foo_webpage', 'key': 'user.xdg.origin.url'},
+            {'path': 'foo_filepath', 'value': b'foo_webpage', 'key': 'user.xdg.referrer.url'}
+        ])
+
+    def test_get_tags(self):
+        # test empty values
+        self.assertEqual(XAttrMetadataPP.get_tags({}), None)
+        self.assertEqual(XAttrMetadataPP.get_tags({'tags': None}), None)
+        self.assertEqual(XAttrMetadataPP.get_tags({'categories': None}), None)
+        self.assertEqual(XAttrMetadataPP.get_tags({'tags': None, 'categories': None}), None)
+
+        # lower-case tags
+        self.assertEqual(XAttrMetadataPP.get_tags({
+            'tags': ['foo', 'FOO'],
+            'categories': ['Foo', 'BAR']
+        }), 'bar,foo'.encode('utf-8'))
+
+        # test tags alone
+        self.assertEqual(XAttrMetadataPP.get_tags({'tags': ['foo']}), 'foo'.encode('utf-8'))
+        self.assertEqual(XAttrMetadataPP.get_tags({'tags': ['foo', 'foo']}), 'foo'.encode('utf-8'))
+        self.assertEqual(XAttrMetadataPP.get_tags({'tags': ['foo', 'bar']}), 'bar,foo'.encode('utf-8'))  # tags are sorted
+
+        # test categories alone
+        self.assertEqual(XAttrMetadataPP.get_tags({'categories': ['foo']}), 'foo'.encode('utf-8'))
+        self.assertEqual(XAttrMetadataPP.get_tags({'categories': ['foo', 'foo']}), 'foo'.encode('utf-8'))
+        self.assertEqual(XAttrMetadataPP.get_tags({'categories': ['foo', 'bar']}), 'bar,foo'.encode('utf-8'))  # tags are sorted
+
+        # test tags + categories
+        self.assertEqual(XAttrMetadataPP.get_tags({'tags': ['foo'], 'categories': None}), 'foo'.encode('utf-8'))
+        self.assertEqual(XAttrMetadataPP.get_tags({'tags': None, 'categories': ['foo']}), 'foo'.encode('utf-8'))
+        self.assertEqual(XAttrMetadataPP.get_tags({'tags': ['foo'], 'categories': ['bar']}), 'bar,foo'.encode('utf-8'))
+        self.assertEqual(XAttrMetadataPP.get_tags({'tags': ['bar'], 'categories': ['foo']}), 'bar,foo'.encode('utf-8'))
+        self.assertEqual(XAttrMetadataPP.get_tags({
+            'tags': ['foo', 'bar'],
+            'categories': ['foo']
+        }), 'bar,foo'.encode('utf-8'))
+        self.assertEqual(XAttrMetadataPP.get_tags({
+            'tags': ['foo', 'bar'],
+            'categories': ['bar', 'foo']
+        }), 'bar,foo'.encode('utf-8'))
+        self.assertEqual(XAttrMetadataPP.get_tags({
+            'tags': ['bar', 'baz'],
+            'categories': ['bar', 'foo']
+        }), 'bar,baz,foo'.encode('utf-8'))
+
+        # test unicode
+        categories = ['H₂O', 'РУ́ССКИЙ', '€ÃĂÀÂÁÅÄ']
+        if sys.version_info.major < 3:
+            categories = ['H₂O'.encode('utf-8'), 'РУ́ССКИЙ'.encode('utf-8'), '€ÃĂÀÂÁÅÄ'.encode('utf-8')]
+
+        self.assertEqual(
+            XAttrMetadataPP.get_tags({'categories': categories}),
+            'h₂o,ру́сский,€ãăàâáåä'.encode('utf-8')
+        )
+
+if __name__ == '__main__':
+    unittest.main()