Add / update tests for predicates in stabiliser sim

Added a new unit test that checks we include the CliffordCircuitPredicate
only when we're running with a stabilizer simulator type (and not
when we have a statevector simulator).

Also update test_simulator to expect to fail on compilation, rather
than breaking on get_result().

tests/integration/backend_test.py

@@ -597,17 +597,11 @@ def test_simulator(
     assert len(stab_counts) == 2
 
     # test non-clifford circuit fails on stabilizer backend
-    # unfortunately the job is accepted, then fails, so have to check get_result
     non_stab_circ = (
         Circuit(2, name="non_stab_circ").H(0).Rx(0.1, 0).CX(0, 1).measure_all()
     )
-    non_stab_circ = stabilizer_backend.get_compiled_circuit(non_stab_circ)
-    broken_handle = stabilizer_backend.process_circuit(
-        non_stab_circ, n_shots, language=language
-    )
-
-    with pytest.raises(GetResultFailed) as _:
-        _ = stabilizer_backend.get_result(broken_handle)
+    with pytest.raises(CircuitNotValidError):
+        _ = stabilizer_backend.get_compiled_circuit(non_stab_circ)
 
 
 @pytest.mark.skipif(skip_remote_tests, reason=REASON)

tests/unit/backend.py

@@ -0,0 +1,26 @@
+import pytest
+from pytket.predicates import CliffordCircuitPredicate
+
+from pytket.extensions.quantinuum import QuantinuumAPIOffline, QuantinuumBackend
+
+
+@pytest.mark.parametrize(
+    "simulator_type,should_have_clifford_predicate",
+    [
+        ("state-vector", False),
+        ("stabilizer", True),
+    ],
+)
+def test_clifford_circuits_for_stabilizer(
+    simulator_type: str,
+    should_have_clifford_predicate: bool,
+) -> None:
+    qapi_offline = QuantinuumAPIOffline()
+    backend = QuantinuumBackend(
+        api_handler=qapi_offline,
+        simulator=simulator_type,
+    )
+    required_predicates = backend.required_predicates
+    assert should_have_clifford_predicate == any(
+        (isinstance(pred, CliffordCircuitPredicate) for pred in required_predicates)
+    )