diff --git a/tests/test_paper.py b/tests/test_paper.py
index 92e0723..9f5c3b3 100644
--- a/tests/test_paper.py
+++ b/tests/test_paper.py
@@ -10,7 +10,34 @@ from pubs.paper import Paper
 class TestAttributes(unittest.TestCase):
 
     def test_tags(self):
-        p = Paper(fixtures.page_bibdata, metadata=fixtures.page_metadata)
+        p = Paper(fixtures.page_bibdata, metadata=fixtures.page_metadata).deepcopy()
         self.assertEqual(p.tags, set(['search', 'network']))
 
+    def test_add_tag(self):
+        p = Paper(fixtures.page_bibdata, metadata=fixtures.page_metadata).deepcopy()
+        p.add_tag('algorithm')
+        self.assertEqual(p.tags, set(['search', 'network', 'algorithm']))
+        p.add_tag('algorithm')
+        self.assertEqual(p.tags, set(['search', 'network', 'algorithm']))
 
+    def test_set_tags(self):
+        p = Paper(fixtures.page_bibdata, metadata=fixtures.page_metadata).deepcopy()
+        p.tags = ['algorithm']
+        self.assertEqual(p.tags, set(['algorithm']))
+
+    def test_remove_tags(self):
+        p = Paper(fixtures.page_bibdata, metadata=fixtures.page_metadata).deepcopy()
+        p.remove_tag('network')
+        self.assertEqual(p.tags, set(['search']))
+
+    def test_mixed_tags(self):
+        p = Paper(fixtures.page_bibdata, metadata=fixtures.page_metadata).deepcopy()
+        p.add_tag('algorithm')
+        self.assertEqual(p.tags, set(['search', 'network', 'algorithm']))
+        p.remove_tag('network')
+        self.assertEqual(p.tags, set(['search', 'algorithm']))
+        p.tags = ['ranking']
+        self.assertEqual(p.tags, set(['ranking']))
+        p.remove_tag('ranking')
+        self.assertEqual(p.tags, set())
+        p.remove_tag('ranking')