diff --git a/tests/test_utils.py b/tests/test_utils.py
index 2064264..c9f6c7f 100644
--- a/tests/test_utils.py
+++ b/tests/test_utils.py
@@ -1,17 +1,30 @@
+"""Test matcher utils."""
+
 from matcher import utils
 
 
-def test_format_wikibase_time_year():
+def test_format_wikibase_time_year() -> None:
+    """Test passing a year to format_wikibase_time."""
     v = {"time": "+1950-00-00T00:00:00Z", "precision": 9}
     assert utils.format_wikibase_time(v) == "1950"
 
 
-def test_format_wikibase_time_century():
+def test_format_wikibase_time_century() -> None:
+    """Test passing centuries to format_wikibase_time."""
     v = {"time": "+0800-00-00T00:00:00Z", "precision": 7}
     assert utils.format_wikibase_time(v) == "8th century"
 
     v = {"time": "+1950-00-00T00:00:00Z", "precision": 7}
     assert utils.format_wikibase_time(v) == "20th century"
 
+
+def test_format_wikibase_time_decade() -> None:
+    """Test passing a full date to format_wikibase_time."""
+    v = {"time": "+1910-00-00T00:00:00Z", "precision": 8}
+    assert utils.format_wikibase_time(v) == "1910s"
+
+
+def test_format_wikibase_time_day() -> None:
+    """Test passing a full date to format_wikibase_time."""
     v = {"time": "+1868-01-09T00:00:00Z", "precision": 11}
     assert utils.format_wikibase_time(v) == "9 January 1868"