Spock: Up and Running

Chapter 15. Testing JavaScript Using Spock

So far, we’ve used Spock exclusively to test Java code. One of the reasons all of the examples in the book use Java is that I want to stress that Spock is able to test more than just Groovy. However, Java is not the only other language that we can test using Spock.

In this chapter, we take a brief look at testing JavaScript using Spock. We’ll use the Nashorn script engine (introduced in Java 8) to evaluate JavaScript and invoke it from Spock.

Nashorn

The Java Virtual Machine (JVM) has long had a JavaScript interpreter—Rhino—shipped along with it, and it has been possible to run simple scripts in the JVM. However, Rhino had some limitations with respect to performance and the interoperability of objects created in Java and JavaScript. Typically, it’s necessary to convert Java objects to a JavaScript representation before passing them to a script running in Rhino and then convert any response value back again.

Nashorn (from the German for “rhino”), introduced alongside Java 8, has fewer such limitations. It is very fast and can in many cases handle regular Java objects passed as arguments to functions. It is necessary to translate lists and arrays to a JavaScript version, but many other structured object types work seamlessly.

Nashorn can also compile JavaScript code for more efficient repeated execution.

Why Test JavaScript from the JVM?

Why would we want to test JavaScript code from the JVM when JavaScript has its own rich suite of ...