diff --git a/src/icalendar/tests/conftest.py b/src/icalendar/tests/conftest.py
index 95a24b2..ee86479 100644
--- a/src/icalendar/tests/conftest.py
+++ b/src/icalendar/tests/conftest.py
@@ -109,6 +109,14 @@ def fuzz_v1_calendar(request):
     return request.param
 
 
+@pytest.fixture()
+def x_sometime():
+    """Map x_sometime to time"""
+    icalendar.cal.types_factory.types_map['X-SOMETIME'] = 'time'
+    yield
+    icalendar.cal.types_factory.types_map.pop('X-SOMETIME')
+
+    
 @pytest.fixture()
 def factory():
     """Return a new component factory."""
diff --git a/src/icalendar/tests/test_time.py b/src/icalendar/tests/test_time.py
index f2aa36c..b31cb7c 100644
--- a/src/icalendar/tests/test_time.py
+++ b/src/icalendar/tests/test_time.py
@@ -1,29 +1,28 @@
-import unittest
-
 import datetime
 import icalendar
 import os
 
+def test_value_type_is_not_mapped():
+    """Usually, the value should be absent."""
+    assert 'X-SOMETIME' not in icalendar.cal.types_factory.types_map
 
-class TestTime(unittest.TestCase):
 
-    def setUp(self):
-        icalendar.cal.types_factory.types_map['X-SOMETIME'] = 'time'
+def test_value_type_is_mapped(x_sometime):
+    """The value is mapped for the test."""
+    assert 'X-SOMETIME' in icalendar.cal.types_factory.types_map
 
-    def tearDown(self):
-        icalendar.cal.types_factory.types_map.pop('X-SOMETIME')
 
-    def test_create_from_ical(self):
-        directory = os.path.dirname(__file__)
-        ics = open(os.path.join(directory, 'calendars', 'time.ics'), 'rb')
-        cal = icalendar.Calendar.from_ical(ics.read())
-        ics.close()
+def test_create_from_ical(x_sometime):
+    directory = os.path.dirname(__file__)
+    ics = open(os.path.join(directory, 'calendars', 'time.ics'), 'rb')
+    cal = icalendar.Calendar.from_ical(ics.read())
+    ics.close()
 
-        self.assertEqual(cal['X-SOMETIME'].dt, datetime.time(17, 20, 10))
-        self.assertEqual(cal['X-SOMETIME'].to_ical(), '172010')
+    assert cal['X-SOMETIME'].dt == datetime.time(17, 20, 10)
+    assert cal['X-SOMETIME'].to_ical() == '172010'
 
-    def test_create_to_ical(self):
-        cal = icalendar.Calendar()
-        cal.add('X-SOMETIME', datetime.time(17, 20, 10))
-        self.assertTrue(b'X-SOMETIME;VALUE=TIME:172010' in
-                        cal.to_ical().splitlines())
+
+def test_create_to_ical(x_sometime):
+    cal = icalendar.Calendar()
+    cal.add('X-SOMETIME', datetime.time(17, 20, 10))
+    assert b'X-SOMETIME;VALUE=TIME:172010' in cal.to_ical().splitlines()