A pyramid metaphor is often used to express the functional granularity or scope of tests since it nicely illustrates, as it gets wider toward the bottom, the number of tests – and thus investment – you should undertake when thinking about your testing strategy. The following diagram shows what this looks like on the Lightning Platform and helps visualize the two unit testing focus areas for this chapter in respect of Apex and Lightning Web Components:

In the following section, we will start at the bottom of this pyramid to better understand what unit testing is and how it can be applied to the Lightning Platform.