test: enable PSR test in test_models_interface

tests/test_models_interfaces.py

@@ -4,13 +4,14 @@
 import numpy as np
 import pytest
 import torch
-from qibo import construct_backend, hamiltonians
+from qibo import hamiltonians
 from qibo.config import raise_error
 from qibo.symbols import Z
 
 import qiboml.models.ansatze as ans
 import qiboml.models.decoding as dec
 import qiboml.models.encoding as enc
+from qiboml.operations.differentiation import PSR
 
 torch.set_default_dtype(torch.float64)
 
@@ -228,6 +229,10 @@ def test_decoding(backend, frontend, layer, seed, analytic):
         pytest.skip("Non pytorch/jax differentiation is not working yet.")
     if analytic and not layer is dec.Expectation:
         pytest.skip("Unused analytic argument.")
+    if not analytic and not layer is dec.Expectation:
+        pytest.skip(
+            "Expectation layer is the only differentiable decoding when the diffrule is not analytical."
+        )
 
     set_seed(frontend, seed)
 
@@ -251,13 +256,19 @@ def test_decoding(backend, frontend, layer, seed, analytic):
         )
         kwargs["observable"] = observable
         kwargs["analytic"] = analytic
+        if not analytic:
+            differentiation_rule = PSR()
+        else:
+            differentiation_rule = None
         kwargs["nshots"] = None
     decoding_layer = layer(nqubits, decoding_qubits, **kwargs)
 
     # if not decoding_layer.analytic:
     #     pytest.skip("PSR differentiation is not working yet.")
 
-    q_model = frontend.QuantumModel(encoding_layer, training_layer, decoding_layer)
+    q_model = frontend.QuantumModel(
+        encoding_layer, training_layer, decoding_layer, differentiation_rule
+    )
 
     data = random_tensor(frontend, (100, dim))
     target = prepare_targets(frontend, q_model, data)