How to make sure your results aren't coming from the browser's cache
If you are testing your shipping methods on your online store, more than likely you've had a lot of repetitive activity. This activity is stored in your browser's cache. Your browser cache is a place on your hard drive where the browser keeps things that it might be able to use again in the future. Retrieving information from your hard drive is faster than retrieving it from the internet.
During repetitive testing, the shipping address and cart content is stored in the browser's cache. If your browser thinks it sees the same shipping address and cart contents it saw previously, it will retrieve the previous rate estimates from its cache. As a result the rates you see in the checkout process won't reflect recent changes made to the app settings or the product shipping parameters.
Option 1: Don't use the same information during checkout
The browser is going to pull a page from cache if it thinks its seen it before. Add different products to the cart or change the address. A simple method we use when performing iterative testing is to change the first name of our fictitious shopper. If George Washington is the name of our fictitious shopper, changing the first name to George A, George B, George C, etc., on each successive test is enough to do the trick.
Option 2: Clear the browsers cache
This option is more invasive because it results in the lost of some or all of your browsing history. However, it can be the preferred method if you want to make sure you aren't retrieving a cached page. How to clear the cache varies by browser. To find out how to clear your browser's cache, Google it.