Testing the Relay environment
There are a few different ways to approach the integration of Relay into a React application. The method we’ll use in this book is the fetchQuery function, which is analogous to the global.fetch function we’ve already used for standard HTTP requests.
However, Relay’s fetchQuery function has a much more complicated setup than global.fetch.
One of the parameters of the fetchQuery function is the environment, and in this section, we’ll see what that is and how to construct it.
Why Do We Need to Construct an Environment?
The Relay environment is an extension point where all manner of functionality can be added. Data caching is one example. If you’re interested in how to do that, check out the Further reading section at the end of this chapter.
We will build a function named buildEnvironment, and then another named getEnvironment that provides a singleton instance of this environment so that the initialization...