diff --git a/tests/test_expectation_maximization.py b/tests/test_expectation_maximization.py
index 9b14649..ba25a20 100644
--- a/tests/test_expectation_maximization.py
+++ b/tests/test_expectation_maximization.py
@@ -90,7 +90,7 @@ def test_grid_SO3_uniform(test_ir, n_particles):
 def test_generate_xy_plane(test_ir, n_pix):
     """Test generation of xy plane."""
     xy_plane = test_ir.generate_xy_plane(n_pix)
-    assert xy_plane.shape == (n_pix ** 2, 3)
+    assert xy_plane.shape == (n_pix**2, 3)
 
 
 def test_generate_slices(test_ir, n_particles, n_pix):
@@ -101,9 +101,9 @@ def test_generate_slices(test_ir, n_particles, n_pix):
 
     slices, xyz_rotated = test_ir.generate_slices(map_3d, xy_plane, n_pix, rots)
 
-    assert xy_plane.shape == (n_pix ** 2, 3)
+    assert xy_plane.shape == (n_pix**2, 3)
     assert slices.shape == (n_particles, n_pix, n_pix)
-    assert xyz_rotated.shape == (n_pix ** 2, 3)
+    assert xyz_rotated.shape == (n_pix**2, 3)
 
 
 def test_apply_ctf_to_slice(test_ir, n_pix):