diff --git a/nac3core/src/toplevel/helper.rs b/nac3core/src/toplevel/helper.rs
index 73325ad5b..2912e3e75 100644
--- a/nac3core/src/toplevel/helper.rs
+++ b/nac3core/src/toplevel/helper.rs
@@ -43,7 +43,12 @@ impl TopLevelDef {
                 "Function {{\nname: {:?},\nsig: {:?},\nvar_id: {:?}\n}}",
                 name,
                 unifier.stringify(*signature, obj_to_name, var_to_name),
-                var_id
+                {
+                    // NOTE: preserve the order for debug output and test
+                    let mut r = var_id.clone();
+                    r.sort_unstable();
+                    r
+                }
             ),
             TopLevelDef::Initializer { class_id } => format!("Initializer {{ {:?} }}", class_id),
         }
diff --git a/nac3core/src/toplevel/mod.rs b/nac3core/src/toplevel/mod.rs
index d5e705823..ce3959825 100644
--- a/nac3core/src/toplevel/mod.rs
+++ b/nac3core/src/toplevel/mod.rs
@@ -588,7 +588,7 @@ impl TopLevelComposer {
         }
 
         println!("type_var_to_concrete_def3: {:?}\n", type_var_to_concrete_def);
-        
+
         // unification of previously assigned typevar
         for (ty, def) in type_var_to_concrete_def {
             println!(
@@ -864,8 +864,7 @@ impl TopLevelComposer {
                             )?
                         };
                         // find type vars within this method parameter type annotation
-                        let type_vars_within =
-                            get_type_var_contained_in_type_annotation(&type_ann);
+                        let type_vars_within = get_type_var_contained_in_type_annotation(&type_ann);
                         // handle the class type var and the method type var
                         for type_var_within in type_vars_within {
                             if let TypeAnnotation::TypeVarKind(ty) = type_var_within {
@@ -987,7 +986,7 @@ impl TopLevelComposer {
                                                 unreachable!("must be type var annotation");
                                             }
                                         }
-                                        
+
                                         // TODO: allow class have field which type refers to Self type?
                                         type_var_to_concrete_def
                                             .insert(dummy_field_type, annotation);
diff --git a/nac3core/src/toplevel/test.rs b/nac3core/src/toplevel/test.rs
index 5de448384..a3bdf1a43 100644
--- a/nac3core/src/toplevel/test.rs
+++ b/nac3core/src/toplevel/test.rs
@@ -342,7 +342,7 @@ fn test_simple_class_analyze(source: Vec<&str>, res: Vec<&str>) {
     let tvar_v = composer
         .unifier
         .get_fresh_var_with_range(&[composer.primitives_ty.bool, composer.primitives_ty.int32]);
-    
+
     println!("t: {}, {:?}", tvar_t.1, tvar_t.0);
     println!("v: {}, {:?}\n", tvar_v.1, tvar_v.0);