TypeScript Setup for REST API Tests

Ahoy, mate!

This topic may be useful for test automation engineers who just started to learn TypeScript. It also extends my previous post:

Minimal REST API tests in Node.js

Dmitrii Bormotov ・ Dec 24 '20 ・ 5 min read

#rest #node #testing #qa

TypeScript is a JavaScript superset in Node.js, which brings static types and other useful features to your project.

Under the hood, it transforms the code you written to the one that your platform understands (ES5 standard).

Source code of project from this article on GitHub: https://github.com/bormando/mochapi/tree/future

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Setup

You may clone a GitHub repo with few example tests from here: https://github.com/bormando/mochapi/tree/main

After cloning, you must execute this command to download all required dependencies:

npm i

To check, if cloned project is working, you may run:

npm run test

It should display something like this in the end:

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Install TypeScript dependencies

These are standard TypeScript dependencies that we'll need to download:

• typescript
• ts-node (to transform code from TypeScript to EcmaScript 5 standard on run)

Also, keep in mind that some Node.js packages like mocha & chai doesn't come with TypeScript, so you'll have to install them separately as well:

• @types/mocha
• @types/chai

To install them all, you'll need to execute in terminal:

npm i -D typescript ts-node @types/mocha @types/chai

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TypeScript configuration

Now, as we've finished dependencies installation, we need to configure TypeScript.

Simply execute npx tsc --init in your project root which will create tsconfig.json.

I recommend these options for new projects:

Don't forget to save changes.

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ES5 vs TypeScript

You may read about base differences between ES5 and TypeScript here:

TypeScript vs. JavaScript. Why was TypeScript developed when we… | by Avelon Pang | Geek Culture | Medium

Avelon Pang ・ Jun 23, 2021 ・

Medium

In our current project, all you'll have to do is:

1. Rename markets.test.js to markets.test.ts.
2. Change imports in markets.test.ts file...

From this:

const axios = require('axios');
const assert = require('chai').assert;

To this:

import axios from 'axios';
import { assert } from 'chai';

These are the small changes but this is all we need to make sure that our TypeScript setup works fine (since this is the point of current article).

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Reconfigure shortcut

Shortcut for running Mocha tests in ES5 looks like this:

"test": "npx mocha src/specs"

You may find it in scripts section inside of package.json file.

To convert code TypeScript code to JavaScript on-run, you need to change this shortcut on something like this:

"test": "npx mocha --require ts-node/register src/specs/**/*.test.ts"

ts-node/register works as a converter in this case.

Also notice src/specs/**/*.test.ts in the end - now we have to specify test files pattern, as Mocha looks for .js files by default.

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Running tests

We're good to go by now, so all you have to do is execute in terminal:

npm test

or

npm run test

And then you must see report in your terminal output:

Thanks for reading, hope you've learned something new.

Comments

[Dmitrii Bormotov]

Glad to help!
Type declaration isn't mandatory - it'll automatically be any.
If I'm correct, this behavior is configurable in tsconfig.json, so it's not necessary to do that in the project presented in the article.