Unit testing is the technique of isolating a single small piece of functionality and testing it independently of the rest of the application and AngularJS. Carefully applied, unit testing can reduce the number of software defects that show up later in the development process, especially those that the user encounters when the application is deployed.
Unit testing works best with teams that have strong design skills and a good understanding of what and who the finished product is for. Without those skills and the broader perspective, the narrow focus that unit testing creates can put too much emphasis on the quality of individual bricks at the cost of the overall structure of the house they are being used to build. The worst possible environment for unit testing is the one in which I encounter it most often: large corporate projects with thousands of developers. In these projects, individual developers have little visibility
of the overarching objectives in anything other than the broadest terms, and passing arbitrary unit tests quickly becomes the sole measure of quality, which requires developers to make assumptions about external inputs to their code that turn out to be wrong. In these situations, a project whose unit test results are positive will get bogged down in integration testing as all of those individual assumptions are discovered and found wanting.
Even so, unit testing can be a powerful tool when applied carefully. Just be sure that you are able to measure the benefit that it brings, that you understand that unit testing triggers the natural inclination of many developers to turn their focus inward, and that passing unit tests doesn’t mean that those units are going to work well together. Use unit testing as part of a broader strategy of end-to-end testing. The AngularJS project recommends Protractor for end- to-end testing, which you can learn about and download from https://github.com/angular/protractor
Source: Freeman Adam (2014), Pro AngularJS (Expert’s Voice in Web Development), Apress; 1st ed. edition.