Test-Driving Service Workers

This chapter looks at service workers, which are bits of code that are installed on the browser and are invoked before any HTTP operation. That makes them useful for a certain set of features, such as enabling offline access to your app. The service worker implemented in this chapter provides exactly that feature.

It’s almost always a good idea to use off-the-shelf service workers rather than rolling your own. But it’s instructive to see how you might test your own service workers, hence the inclusion in this book.

The term testability is used to describe how straightforward it is to write tests for your application code. The way we structure our components and modules has a big impact on their testability. Service workers are a great example of taking something that, at first glance, is a highly complex thing to test and restructuring its implementation so that the tests become almost trivial.

This chapter covers the following key...