diff --git a/test/test_direction.py b/test/test_direction.py
index dce9c26..e9d07be 100644
--- a/test/test_direction.py
+++ b/test/test_direction.py
@@ -8,28 +8,27 @@ import numpy as np
 from roentgen.direction import parse_vector
 
 
-def test_compass_points_1():
+def test_compass_points_1() -> None:
     """ Test north direction. """
     assert np.allclose(parse_vector("N"), np.array([0, -1]))
 
 
-def test_compass_points_2():
+def test_compass_points_2() -> None:
     """ Test north-west direction. """
     root: np.float64 = -np.sqrt(2) / 2
     assert np.allclose(parse_vector("NW"), np.array([root, root]))
 
 
-def test_compass_points_3():
+def test_compass_points_3() -> None:
     """ Test south-south-west direction. """
-    assert np.allclose(
-        parse_vector("SSW"), np.array([-0.38268343, 0.92387953]))
+    assert np.allclose(parse_vector("SSW"), np.array([-0.38268343, 0.92387953]))
 
 
-def test_invalid():
+def test_invalid() -> None:
     """ Test invalid direction representation string. """
     assert not parse_vector("O")
 
 
-def test_degree():
+def test_degree() -> None:
     """ Test east direction. """
     assert np.allclose(parse_vector("90"), np.array([1, 0]))