The only dependency we'll use for this example is Jest, a JavaScript testing framework built by Facebook. Jest is an excellent choice for testing because it includes most of the features you'll need out of the box, such as coverage, assertions, and mocking. In most cases, you can use it with zero configuration, depending on the complexity of your application. If you're interested in learning more, check out Jest's website at https://jestjs.io. Open a terminal instance in the /chapter-09-node/testing-example folder and run the following command to install Jest:

npm install

In the package.json file, there are three entries in the scripts section: build, pretest, and test. The build script executes the emcc command with the required flags to compile /src/main.c to /src/main.wasm. The test script executes the jest command with the --verbose flag, which provides additional details for each of the test suites. The pretest script simply runs the build script to ensure /src/main.wasm exists prior to running any tests.