test: enable ut without torch

tests/quafu/algorithms/ansatz_test.py

@@ -14,7 +14,7 @@
 """TODO: test of ansatz needs improvement once ansatz has more featuers"""
 
 import numpy as np
-from quafu.algorithms.ansatz import AlterLayeredAnsatz, QAOAAnsatz, QuantumNeuralNetwork
+from quafu.algorithms.ansatz import AlterLayeredAnsatz, QAOAAnsatz
 from quafu.algorithms.hamiltonian import Hamiltonian, PauliOp
 
 
@@ -37,8 +37,3 @@ def test_build(self):
         circ = AlterLayeredAnsatz(4, 4)
         # print("\n ::: testing ::: \n")
         # circ.plot_circuit(save_path="TestAlterLayeredAnsatz.svg")
-
-
-class TestQuantumNeuralNetwork:
-    def test_build(self):
-        circ = QuantumNeuralNetwork(2, [])

tests/quafu/algorithms/construct_qlayers_test.py

@@ -11,6 +11,9 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+import pytest
+
+pytest.importorskip("torch")
 import numpy as np
 from quafu.algorithms import AmplitudeEmbedding, AngleEmbedding
 from quafu.algorithms.ansatz import QuantumNeuralNetwork

tests/quafu/algorithms/qnn_test.py

@@ -13,6 +13,8 @@
 # limitations under the License.
 import numpy as np
 import pytest
+
+pytest.importorskip("torch")
 import torch
 from quafu.algorithms.ansatz import QuantumNeuralNetwork
 from quafu.algorithms.gradients import compute_vjp, jacobian
@@ -112,6 +114,7 @@ def forward(self, features):
     #         yield nn.Parameter(p)
 
 
+@pytest.importorskip("torch")
 class TestLayers:
     circ = QuantumCircuit(2)
     theta = [Parameter(f"theta_{i}", 0.1) for i in range(3)]