diff --git a/litebird_sim/quaternions.py b/litebird_sim/quaternions.py
index a79d0cce..d8504466 100644
--- a/litebird_sim/quaternions.py
+++ b/litebird_sim/quaternions.py
@@ -501,17 +501,6 @@ def quat_rotation_brdcast(theta_rad, vec_matrix):
         [vec_matrix * s, np.cos(theta_rad / 2) * np.ones((vec_matrix.shape[0], 1))]
     )
 
-def quat_rotation_brdcast_single_axis(theta_rad_array, vec):
-    """This function rotates a quaternion by theta_rad about a specific axis.
-    Args:
-        theta_rad_array (numpy.array): The angles to rotate the quaternion by in radians.
-        vec (numpy.array[3]): The vector to rotate the quaternion about.
-    """
-    s = np.sin(theta_rad_array / 2)
-    c = np.cos(theta_rad_array / 2)
-    return np.hstack(
-        [vec * s[:, np.newaxis], c[:, np.newaxis]]
-    )
 
 def quat_rotation_x_brdcast(theta_rad_array):
     """Return a quaternion representing a rotation around the x axis
diff --git a/litebird_sim/scanning.py b/litebird_sim/scanning.py
index 731bc9f4..53ca9e21 100644
--- a/litebird_sim/scanning.py
+++ b/litebird_sim/scanning.py
@@ -483,19 +483,19 @@ def __mul__(self, other: "RotQuaternion") -> "RotQuaternion":
             assert (
                 self.quats.shape == other.quats.shape
             ), f"quaternions have different shapes: {self.quats.shape} vs {other.quats.shape}"
-            assert (
-                isinstance(self.start_time, type(other.start_time))
+            assert isinstance(
+                self.start_time, type(other.start_time)
             ), f"start_time must have the same type: {type(self.start_time)} vs {type(other.start_time)}"
             if isinstance(self.start_time, float):
-                assert (
-                    np.isclose(self.start_time, other.start_time)
+                assert np.isclose(
+                    self.start_time, other.start_time
                 ), f"start_time must be the same value: {self.start_time} vs {other.start_time}"
             else:
                 assert (
                     self.start_time == other.start_time
                 ), f"start_time must be the same value: {self.start_time} vs {other.start_time}"
-            assert (
-                np.isclose(self.sampling_rate_hz, other.sampling_rate_hz)
+            assert np.isclose(
+                self.sampling_rate_hz, other.sampling_rate_hz
             ), f"sampling_rate_hz must be the same value: {self.sampling_rate_hz} vs {other.sampling_rate_hz}"
 
             result_start_time = self.start_time
@@ -540,12 +540,14 @@ def conj(self):
         return RotQuaternion(
             start_time=self.start_time,
             sampling_rate_hz=self.sampling_rate_hz,
-            quats=np.array([
-                -self.quats[:,0],
-                -self.quats[:,1],
-                -self.quats[:,2],
-                self.quats[:,3]
-                ]),
+            quats=np.array(
+                [
+                    -self.quats[:, 0],
+                    -self.quats[:, 1],
+                    -self.quats[:, 2],
+                    self.quats[:, 3],
+                ]
+            ),
         )
 
     def slerp(
diff --git a/test/test_pointing_sys.py b/test/test_pointing_sys.py
index 714c5c56..11c62bdb 100644
--- a/test/test_pointing_sys.py
+++ b/test/test_pointing_sys.py
@@ -10,7 +10,7 @@
 
 import litebird_sim as lbs
 
-make_reference_file = False # if True, generate reference file at `path_of_reference`.
+make_reference_file = False  # if True, generate reference file at `path_of_reference`.
 
 telescopes = ["LFT", "MFT", "HFT"]
 start_time = 0
@@ -271,7 +271,6 @@ def test_PointingSys_add_single_offset_to_spacecraft(
     axis = "x"
     pointing_sys.spacecraft.add_offset(single_offset, axis)
 
-
     lbs.prepare_pointings(
         sim.observations, sim.instrument, sim.spin2ecliptic_quats, hwp=sim.hwp
     )
@@ -314,7 +313,6 @@ def test_PointingSys_add_common_disturb_to_spacecraft(
     axis = "x"
     pointing_sys.spacecraft.add_disturb(noise_rad_1d_array, axis)
 
-
     lbs.prepare_pointings(
         sim.observations, sim.instrument, sim.spin2ecliptic_quats, hwp=sim.hwp
     )
@@ -339,6 +337,7 @@ def test_PointingSys_add_common_disturb_to_spacecraft(
             atol=atol,
         )
 
+
 @pytest.mark.parametrize("telescope", telescopes)
 def test_PointingSys_add_hwp_rot_disturb(
     telescope, make_reference_file=make_reference_file
@@ -354,10 +353,11 @@ def test_PointingSys_add_hwp_rot_disturb(
     wedge_angle_rad = np.deg2rad(1.0)
     refractive_idx = 3.1
     tilt_angle_rad = pointing_sys.hwp.get_wedgeHWP_pointing_shift_angle(
-        wedge_angle_rad,
-        refractive_idx
+        wedge_angle_rad, refractive_idx
+    )
+    pointing_sys.hwp.add_hwp_rot_disturb(
+        tilt_angle_rad, ang_speed_radpsec, tilt_phase_rad
     )
-    pointing_sys.hwp.add_hwp_rot_disturb(tilt_angle_rad, ang_speed_radpsec, tilt_phase_rad)
 
     lbs.prepare_pointings(
         sim.observations, sim.instrument, sim.spin2ecliptic_quats, hwp=sim.hwp