Cover auto solver default

Author: ctoth

tests/test_solver_availability.py

@@ -37,7 +37,7 @@
 }
 
 
-def test_solve_dung_extensions_returns_extensions_for_default_native_backend() -> None:
+def test_solve_dung_extensions_defaults_to_auto_backend() -> None:
     framework = ArgumentationFramework(
         arguments=frozenset({"a", "b"}),
         defeats=frozenset({("a", "b")}),
@@ -49,6 +49,23 @@ def test_solve_dung_extensions_returns_extensions_for_default_native_backend() -
     assert result.extensions == (frozenset({"a"}),)
 
 
+def test_solve_dung_extensions_default_auto_uses_sat_for_stable(monkeypatch) -> None:
+    framework = ArgumentationFramework(
+        arguments=frozenset({"a", "b"}),
+        defeats=frozenset({("a", "b")}),
+    )
+
+    def forbidden_native_extensions(*args, **kwargs):
+        raise AssertionError("default stable solving should not call native enumeration")
+
+    monkeypatch.setattr(solver_module, "_dung_extensions", forbidden_native_extensions)
+
+    result = solve_dung_extensions(framework, semantics="stable")
+
+    assert isinstance(result, ExtensionSolverSuccess)
+    assert result.extensions == (frozenset({"a"}),)
+
+
 @given(
     argumentation_frameworks(max_args=4),
     st.sampled_from(sorted(NATIVE_EXTENSION_ORACLES)),