React: Building Modern Web Applications

Installing and running Jest

First, let's install the Jest command-line interface (Jest CLI):

npm install –-save-dev jest-cli

This command installs the Jest CLI, and adds it as a development dependency to our ~/snapterest/package.json file. Next, let's edit the package.json file. We'll replace the existing "script" object:

"scripts": {
  "test": "echo \"Error: no test specified\" && exit 1"
},

Replace the preceding object with the following one:

"scripts": {
  "test": "jest"
},

Now we're ready to run our test suit. Navigate to the ~/snapterest/ directory, and run the following command:

npm test

You should see the following message in your Terminal:

Using Jest CLI v0.4.18
 PASS  source/utils/__tests__/TweetUtils-test.js (0.065s)
1 test passed (1 total)