Update plugin: XEP-0317 (hats)

Merge changes from nicoco's MR that I missed, improving tests and
interface.

tests/test_stanza_xep_0317.py

@@ -2,16 +2,15 @@ import unittest
 from slixmpp import Presence
 from slixmpp.test import SlixTest
 import slixmpp.plugins.xep_0317 as xep_0317
-from slixmpp.xmlstream import register_stanza_plugin
+from slixmpp.plugins.xep_0317 import stanza
 
 
 class TestStanzaHats(SlixTest):
 
     def setUp(self):
-        register_stanza_plugin(Presence, xep_0317.Hats)
-        register_stanza_plugin(xep_0317.Hats, xep_0317.Hats)
+        stanza.register_plugin()
 
-    def testCreateHats(self):
+    def test_create_hats(self):
         raw_xml = """
           <hats xmlns="urn:xmpp:hats:0">
             <hat uri="http://example.com/hats#Teacher" title="Teacher"/>
@@ -27,5 +26,42 @@ class TestStanzaHats(SlixTest):
 
         self.check(hats, raw_xml, use_values=False)
 
+    def test_set_single_hat(self):
+        presence = Presence()
+        presence["hats"]["hat"]["uri"] = "test-uri"
+        presence["hats"]["hat"]["title"] = "test-title"
+        self.check(
+            presence,  # language=XML
+            """
+            <presence>
+              <hats xmlns='urn:xmpp:hats:0'>
+                <hat uri='test-uri' title='test-title'/>
+              </hats>
+            </presence>
+            """,
+        )
+
+    def test_set_multi_hat(self):
+        presence = Presence()
+        presence["hats"].add_hats([("uri1", "title1"), ("uri2", "title2")])
+        self.check(
+            presence,  # language=XML
+            """
+            <presence>
+              <hats xmlns='urn:xmpp:hats:0'>
+                <hat uri='uri1' title='title1'/>
+                <hat uri='uri2' title='title2'/>
+              </hats>
+            </presence>
+            """,
+        )
+
+    def test_get_hats(self):
+        presence = Presence()
+        presence["hats"].add_hats([("uri1", "title1"), ("uri2", "title2")])
+        for i, hat in enumerate(presence["hats"]["hats"], start=1):
+            self.assertEqual(hat["uri"], f"uri{i}")
+            self.assertEqual(hat["title"], f"title{i}")
+
 
 suite = unittest.TestLoader().loadTestsFromTestCase(TestStanzaHats)