What Is Cache and Why Is It Important in Testing?

A cache is temporary storage for data (determined by the website creator) from the visited web page.

First of all, many elements on the web pages are the same: images, HTML, CSS, JavaScript, and there is no point in reloading them every time. Second of all, when you reopen the same page, the same logic applies – these elements have already been loaded, so there is no need to do that again every time. Saving web page data on your computer instead of reloading it helps save web browsing time and bandwidth, but on the other hand, reduces the lifespan of SSDs, so you can always turn off caching in your browser entirely.

Types of Caching

Browser caching. The user’s device makes and stores a copy of various elements of the website. These can be scripts, text, or images. When you open a page, the browser cache helps to load all this much faster.

Caching on the server. All data is stored on the server. It stores the results of queries, which helps to avoid reprocessing the same information from the user.

In testing, in almost all cases, the rule is to clear the cache after each test pass (unless this is a purposeful test of the cache itself or the presence of a cache is required for some reason). The fact is that the cache obviously distorts the performance testing indicators, and can also cause a false bug report due to obsolete or inconsistent actual and stored data. In some cases, you cannot do without clearing the cache, even simply because of the huge amount of cached data.