diff --git a/tests/test_cuquantum_cutensor_backend.py b/tests/test_cuquantum_cutensor_backend.py
index 19a81a8..0cbfcc4 100644
--- a/tests/test_cuquantum_cutensor_backend.py
+++ b/tests/test_cuquantum_cutensor_backend.py
@@ -9,6 +9,7 @@ from qibo.symbols import X, Z
 
 ABS_TOL = 1e-7
 
+
 def qibo_qft(nqubits, swaps):
     circ_qibo = QFT(nqubits, swaps)
     state_vec = circ_qibo().state(numpy=True)
@@ -166,7 +167,9 @@ def test_expectation(nqubits: int, dtype="complex128"):
     }
     backend.configure_tn_simulation(computation_settings_1)
     result_tn = backend.execute_circuit(circuit=qibo_circ)
-    assert math.isclose(exact_expval.item(), result_tn.real.get().item(), abs_tol=ABS_TOL)
+    assert math.isclose(
+        exact_expval.item(), result_tn.real.get().item(), abs_tol=ABS_TOL
+    )
 
     # Test with user defined hamiltonian using "hamiltonians.SymbolicHamiltonian" object.
     computation_settings_2 = {
@@ -177,7 +180,9 @@ def test_expectation(nqubits: int, dtype="complex128"):
     }
     backend.configure_tn_simulation(computation_settings_2)
     result_tn = backend.execute_circuit(circuit=qibo_circ)
-    assert math.isclose(exact_expval.item(), result_tn.real.get().item(), abs_tol=ABS_TOL)
+    assert math.isclose(
+        exact_expval.item(), result_tn.real.get().item(), abs_tol=ABS_TOL
+    )
 
     # Test with user defined hamiltonian using Dictionary object form of hamiltonian.
     ham_dict = build_observable_dict(nqubits)
@@ -189,4 +194,6 @@ def test_expectation(nqubits: int, dtype="complex128"):
     }
     backend.configure_tn_simulation(computation_settings_3)
     result_tn = backend.execute_circuit(circuit=qibo_circ)
-    assert math.isclose(exact_expval.item(), result_tn.real.get().item(), abs_tol=ABS_TOL)
+    assert math.isclose(
+        exact_expval.item(), result_tn.real.get().item(), abs_tol=ABS_TOL
+    )
diff --git a/tests/test_cuquantum_cutensor_mpi_backend.py b/tests/test_cuquantum_cutensor_mpi_backend.py
index 0e2fcef..459a5cc 100644
--- a/tests/test_cuquantum_cutensor_mpi_backend.py
+++ b/tests/test_cuquantum_cutensor_mpi_backend.py
@@ -12,6 +12,7 @@ from qibo.symbols import X, Z
 
 ABS_TOL = 1e-7
 
+
 def qibo_qft(nqubits, swaps):
     circ_qibo = QFT(nqubits, swaps)
     state_vec = circ_qibo().state(numpy=True)