Only add axioms for testing functions

Author: romainbrenguier

src/solvers/refinement/string_refinement_util.cpp

@@ -399,7 +399,10 @@ void string_dependenciest::add_constraints(
 {
   for(const auto &builtin : builtin_function_nodes)
   {
-    const exprt return_value = builtin.data->add_constraints(generator);
-    generator.add_lemma(equal_exprt(return_value, builtin.data->return_code));
+    if(builtin.data->maybe_testing_function())
+    {
+      const exprt return_value = builtin.data->add_constraints(generator);
+      generator.add_lemma(equal_exprt(return_value, builtin.data->return_code));
+    }
   }
 }