Testing Framework - spyOn() problem on Firefox. #150

Hi, I've faced a problem testing the cartTest.js code with Jasmine 5.4.0 on Firefox, as it gave an error

Error: <spyOn> : Can't spy on setItem because assigning to it had no effect

At first, I thought something was wrong with my code, so I copied the code from the uploaded file and rerun the test. However, the error persisted. I searched and found that this problem occurs on some browsers, i.e. Firefox and Safari (https://jasmine.github.io/pages/faq.html#localstorage), but I didn't understand how the solution worked. Could you please help me solve this problem? Thank you