diff --git a/tests/test_channel_metrics/test_completely_bounded_trace_norm.py b/tests/test_channel_metrics/test_completely_bounded_trace_norm.py
index a5ca7f74..becd6b37 100644
--- a/tests/test_channel_metrics/test_completely_bounded_trace_norm.py
+++ b/tests/test_channel_metrics/test_completely_bounded_trace_norm.py
@@ -20,8 +20,7 @@ def test_cb_trace_norm_CP():
 
 
 def test_cb_trace_norm_unitaries_channel():
-    """The diamond norm of phi = id- U id U* is the diameter of the smallest circle
-    that contains the eigenvalues of U."""
+    """The diamond norm of phi = id- U id U* is the diameter of the smallest circle that contains the eigenvalues of U."""
     U = 1 / np.sqrt(2) * np.array([[1, 1], [-1, 1]])  # Hadamard gate
     phi = kraus_to_choi([[np.eye(2), np.eye(2)], [U, -U]])
     lam, _ = np.linalg.eig(U)