@kronoslive/codeceptjs/docs/typescript.md

Supercharged End 2 End Testing Framework for NodeJS

---
permalink: /typescript
title: TypeScript
---

# TypeScript

CodeceptJS supports [type declaration](https://github.com/codecept-js/CodeceptJS/tree/master/typings) for [TypeScript](https://www.typescriptlang.org/). It means that you can write your tests in TS. Also, all of your custom steps can be written in TS

# Why TypeScript?

With the TypeScript writing CodeceptJS tests becomes much easier. If you configure TS properly in your project as well as your IDE, you will get the following features:
- [Autocomplete (with InteliSence)](https://code.visualstudio.com/docs/editor/intellisense) - a tool that streamlines your work by suggesting when you typing what function or property which exists in a class, what arguments can be passed to that method, what it returns, etc.
Example:

![Auto Complete](/img/Auto_comlete.gif)

- To show additional information for a step in a test. Example:

![Quick Info](/img/Quick_info.gif)

- Checks types - thanks to TypeScript support in CodeceptJS now allow to tests your tests. TypeScript can prevent some errors: 
  - invalid type of variables passed to function;
  - calls no-exist method from PageObject or `I` object;
  - incorrectly used CodeceptJS features; 


## Getting Started

### TypeScript Boilerplate

To get started faster we prepared [typescript boilerplate project](https://github.com/codeceptjs/typescript-boilerplate) which can be used instead of configuring TypeScript on your own. Clone this repository into an empty folder and you are done.

Otherwise, follow next steps to introduce TypeScript into the project.

### Install TypeScipt

For writing tests in TypeScript you'll need to install `typescript` and `ts-node` into your project.

```
npm install typescript ts-node
```

### Configure codecept.conf.js

To configure TypeScript in your project, you need to add [`ts-node/register`](https://github.com/TypeStrong/ts-node) on first line in your config. Like in the following config file:

```js
require('ts-node/register')

exports.config = {
  tests: './*_test.ts',
  output: './output',
  helpers: {
    Puppeteer: {
      url: 'http://example.com',
    },
  },
  name: 'project name',
}
```

### Configure tsconfig.json

We recommended the following configuration in a [tsconfig.json](https://www.typescriptlang.org/docs/handbook/tsconfig-json.html):

```json
{
  "ts-node": {
    "files": true
  },
  "compilerOptions": {
    "target": "es2018",
    "lib": ["es2018", "DOM"],
    "esModuleInterop": true,
    "module": "commonjs",
    "strictNullChecks": true,
    "types": ["codeceptjs"],
  },
}
```

> You can find an example project with TypeScript and CodeceptJS on our project [typescript-boilerplate](https://github.com/codecept-js/typescript-boilerplate).

### Set Up steps.d.ts

Configuring the `tsconfig.json` and `codecept.conf.js` is not enough, you will need to configure the `steps.d.ts` file for custom steps. Just simply do this by running this command::

`npx codeceptjs def`

As a result, a file will be created on your root folder with following content:

```ts
/// <reference types='codeceptjs' />

declare namespace CodeceptJS {
  interface SupportObject { I: I }
  interface Methods extends Puppeteer {}
  interface I extends WithTranslation<Methods> {}
  namespace Translation {
    interface Actions {}
  }
}

```

## Types for custom helper or page object

If you want to get types for your [custom helper](https://codecept.io/helpers/#configuration), you can add their automatically with CodeceptJS command `npx codeceptjs def`. 

For example, if you add the new step `printMessage` for your custom helper like this:
```js
// customHelper.ts
class CustomHelper extends Helper {
  printMessage(msg: string) {
    console.log(msg)
  }
}

export = CustomHelper
```

Then you need to add this helper to your `codecept.conf.js` like in this [docs](https://codecept.io/helpers/#configuration).
And then run the command `npx codeceptjs def`. 

As result our `steps.d.ts` file will be updated like this: 
```ts
/// <reference types='codeceptjs' />
type CustomHelper = import('./CustomHelper');

declare namespace CodeceptJS {
  interface SupportObject { I: I }
  interface Methods extends Puppeteer, CustomHelper {}
  interface I extends WithTranslation<Methods> {}
  namespace Translation {
    interface Actions {}
  }
}
```

And now you can use autocomplete on your test.

Generation types for PageObject looks like for a custom helper, but `steps.d.ts` will look like:
```ts
/// <reference types='codeceptjs' />
type loginPage = typeof import('./loginPage');
type homePage = typeof import('./homePage');
type CustomHelper = import('./CustomHelper');

declare namespace CodeceptJS {
  interface SupportObject { I: I, loginPage: loginPage, homePage: homePage }
  interface Methods extends Puppeteer, CustomHelper {}
  interface I extends WithTranslation<Methods> {}
  namespace Translation {
    interface Actions {}
  }
}
```