test(undo-redo): explain why first update after clearing cannot be undone

Author: GregOnNet

libs/ngrx-toolkit/src/lib/with-undo-redo.spec.ts

@@ -254,31 +254,30 @@ describe('withUndoRedo', () => {
     });
 
     it('can undo after clearing and setting the same value again', fakeAsync(() => {
-      const recordState = { customer: { firstname: 'Santa' } };
-
       const Store = signalStore(
         { providedIn: 'root' },
-        withState(recordState),
+        withState(testState),
         withMethods((store) => ({
-          update: (value: typeof recordState) => patchState(store, value),
+          update: (value: string) => patchState(store, { test: value }),
         })),
-        withUndoRedo({ keys: ['customer'] })
+        withUndoRedo({ keys: testKeys })
       );
 
       const store = TestBed.inject(Store);
 
-      store.update({ customer: { firstname: 'Alan' } });
+      store.update('Alan');
       tick(1);
 
-      store.update({ customer: { firstname: 'Gordon' } });
+      store.update('Gordon');
       tick(1);
 
       store.clearStack();
       tick(1);
 
-      // After clearing the undo/redo stack, there is no previous item any more
-      // The following update is the very first value.
-      store.update({ customer: { firstname: 'Hugh' } });
+      // After clearing the undo/redo stack, there is no previous item anymore.
+      // The following update becomes the first value.
+      // Since there is no other value before, it cannot be undone.
+      store.update('Hugh');
       tick(1);
 
       expect(store.canUndo()).toBe(false);