Jest has become one of the most popular solutions when unit testing in Node: let's see why.

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Unit tests improve the reliability and robustness of backend applications. Jest is a popular, free JavaScript testing framework known for its intuitive API, zero-configuration approach, and native integration with tools like Babel and Webpack. Jest supports writing unit, integration, and snapshot tests in JavaScript and TypeScript. Its main features include an intuitive BDD-like API, human-readable assertions, high configurability, and robust mocking capabilities. To integrate Jest into a Node.js project, one needs to install Jest, set up a configuration file, organize test files, and run tests to verify their functionality. Advanced users can explore Jest's extensive documentation and community resources for more in-depth guidance and support.

Unit Testing in Node.js With Jest

Exploring Jest: Features, Capabilities, and Core Aspects

Integrating Jest into Node.js for Unit Testing

Jest is not a good fit to reliably test Node.js backend applications. Unfortunately, Jest patches Node.js globals, and these <a href="https://github.com/jestjs/jest/issues/2549" target="_blank" rel="noopener nofollow">currently differ</a> which means that test checking for example for <code>instance of</code> etc. may fail. So, you are not guaranteed that if a test passes with Jest, your code will then run fine in production.
Here is an example taken from a <a href="https://twitter.com/matteocollina/status/1600058525916360704" target="_blank" rel="noopener nofollow">Matteo Collina’s tweet</a>
<pre><code class="language-js">const { readFileSync } = require(&#x27;node:fs&#x27;)

test(&#x27;Error&#x27;, () =&gt; {
 try {
 readFileSync(&#x27;non-existent-file&#x27;);
 }
 catch(e) {
 expect(e).toBeInstanceOf(Error);
 }
})
</code></pre>
This test fails, as the Error class globally provided by Jest differs from the one provided by Node
Nowadays, for backend applications it is highly recommended to use something else, and the best suggestion is the test runner provided directly by Node.js. It is now marked as stable in all LTS versions of node currently in maintenance/active development and it is reliable for testing backend applications.
Same example as above, but with node test runner
<pre><code class="language-js">const { readFileSync } = require(&#x27;node:fs&#x27;);
const { test } = require(&#x27;node:test&#x27;);
const assert = require(&#x27;node:assert&#x27;);

test(&#x27;Error&#x27;, () =&gt; {
 try {
 readFileSync(&#x27;non-existent-file&#x27;);
 }
 catch(e) {
 assert.strict.ok(e instanceof Error)
 }
})
</code></pre>
Jest is good for front end test

Ottima stesura e di facile comprensione. Complimenti!