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https://github.com/mattphillips/babel-jest-assertions
Babel Plugin that adds safety to your tests by verifying assertions are actually ran 🃏⁉️
https://github.com/mattphillips/babel-jest-assertions
assertion babel babel-plugin jest testing
Last synced: about 1 month ago
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Babel Plugin that adds safety to your tests by verifying assertions are actually ran 🃏⁉️
- Host: GitHub
- URL: https://github.com/mattphillips/babel-jest-assertions
- Owner: mattphillips
- License: mit
- Created: 2017-09-13T11:33:58.000Z (about 7 years ago)
- Default Branch: master
- Last Pushed: 2023-01-11T18:46:46.000Z (almost 2 years ago)
- Last Synced: 2024-10-15T18:41:08.357Z (about 2 months ago)
- Topics: assertion, babel, babel-plugin, jest, testing
- Language: JavaScript
- Homepage: https://www.npmjs.com/package/babel-jest-assertions
- Size: 588 KB
- Stars: 96
- Watchers: 3
- Forks: 3
- Open Issues: 21
-
Metadata Files:
- Readme: README.md
- Contributing: CONTRIBUTING.md
- Funding: .github/FUNDING.yml
- License: LICENSE
Awesome Lists containing this project
- awesome-jest - babel-jest-assertions
README
babel-jest-assertions
🃏⁉️
Adds expect.assertions(n) and expect.hasAssertions to all tests automatically
[](https://travis-ci.org/mattphillips/babel-jest-assertions)
[](https://codecov.io/github/mattphillips/babel-jest-assertions)
[](https://www.npmjs.com/package/babel-jest-assertions)
[](http://npm-stat.com/charts.html?package=babel-jest-assertions&from=2017-09-14)
[](https://github.com/mattphillips/babel-jest-assertions/blob/master/LICENSE)
[](http://makeapullrequest.com)
[](https://github.com/mattphillips/babel-jest-assertions/blob/master/docs/ROADMAP.md)
[](https://github.com/mattphillips/babel-jest-assertions/blob/master/docs/EXAMPLES.md)
## Problem
Ever wondered if your tests are actually running their assertions, especially in asynchronous tests? Jest has two features
built in to help with this: [`expect.assertions(number)`](https://facebook.github.io/jest/docs/en/expect.html#expectassertionsnumber)
and [`expect.hasAssertions()`](https://facebook.github.io/jest/docs/en/expect.html#expecthasassertions). These can be
useful when doing something like:
```js
it('resolves to one', () => {
Promise.reject(1).then(value => expect(value).toBe(1));
});
```
The issue here is the `catch` case is not dealt with in this test, _which is fine as we are testing the happy path_,
but this test will currently pass even though the `Promise` rejects and the assertion is never ran.
## Solution
One solution is to manually adjust the above test to include `expect.assertions(number)` and `expect.hasAssertions()`
this is quite verbose and prone to human error.
An alternative is a babel plugin to automate adding these additional properties, and this is such plugin 😉
## Installation
With npm:
```sh
npm install --save-dev babel-jest-assertions
```
With yarn:
```sh
yarn add -D babel-jest-assertions
```
## Setup
### .babelrc
```json
{
"plugins": ["babel-jest-assertions"]
}
```
### CLI
```sh
babel --plugins babel-jest-assertions script.js
```
### Node
```javascript
require('babel-core').transform('code', {
plugins: ['babel-jest-assertions'],
})
```
## Usage
Simply write your tests as you would normally and this plugin will add the verification of assertions in the background.
**One assertion**
```js
it('resolves to one', () => {
Promise.reject(1).then(value => expect(value).toBe(1));
});
```
`↓ ↓ ↓ ↓ ↓ ↓`
```js
it('resolves to one', () => {
expect.hasAssertions();
expect.assertions(1);
Promise.reject(1).then(value => expect(value).toBe(1));
});
```
_Note_: this test will now fail 🎉
**Multiple assertions**
```js
it('counts multiple assertions too', () => {
expect(1 + 0).toBe(1);
expect(0 + 1).toBe(1);
});
```
`↓ ↓ ↓ ↓ ↓ ↓`
```js
it('counts multiple assertions too', () => {
expect.hasAssertions();
expect.assertions(2);
expect(1 + 0).toBe(1);
expect(0 + 1).toBe(1);
});
```
**Asynchronous assertions**
```js
it('counts multiple assertions too', async () => {
const res = await fetch('www.example.com');
expect(res.json).toBeTruthy();
const json = await res.json();
expect(json).toEqual({ whatever: 'trevor' });
});
```
`↓ ↓ ↓ ↓ ↓ ↓`
```js
it('counts multiple assertions too', async () => {
expect.hasAssertions();
expect.assertions(2);
const res = await fetch('www.example.com');
expect(res.json).toBeTruthy();
const json = await res.json();
expect(json).toEqual({ whatever: 'trevor' });
});
```
**beforeEach and afterEach blocks**
If you have expectations inside either of `beforeEach` or `afterEach` blocks for your test then these expects will be
included in the count - even if you have nested describe blocks each with their own `beforeEach`/`afterEach` the count
will accumulate.
```js
beforeEach(() => {
expect(true).toBe(true);
});
afterEach(() => {
expect(true).toBe(true);
});
describe('.add', () => {
beforeEach(() => {
expect(true).toBe(true);
});
afterEach(() => {
expect(true).toBe(true);
});
it('returns 1 when given 0 and 1', () => {
expect(add(1, 0)).toEqual(1);
});
describe('.add2', () => {
beforeEach(() => {
expect(true).toBe(true);
});
afterEach(() => {
expect(true).toBe(true);
});
it('returns 1 when given 0 and 1', () => {
expect(add2(1, 0)).toEqual(1);
});
});
});
↓ ↓ ↓ ↓ ↓ ↓
beforeEach(() => {
expect(true).toBe(true);
});
afterEach(() => {
expect(true).toBe(true);
});
describe('.add', () => {
beforeEach(() => {
expect(true).toBe(true);
});
afterEach(() => {
expect(true).toBe(true);
});
it('returns 1 when given 0 and 1', () => {
expect.assertions(5);
expect.hasAssertions();
expect(add2(1, 0)).toEqual(1);
});
describe('.add2', () => {
beforeEach(() => {
expect(true).toBe(true);
});
afterEach(() => {
expect(true).toBe(true);
});
it('returns 1 when given 0 and 1', () => {
expect.assertions(7);
expect.hasAssertions();
expect(add2(1, 0)).toEqual(1);
});
});
});
```
**Comments are ignored**
```js
it('ignores commented-out assertions', async () => {
const res = await fetch('www.example.com');
// expect(res.json).toBeTruthy();
const json = await res.json();
/*
expect(json).toEqual({ whatever: 'trevor1' });
*/
expect(json).toEqual({ whatever: 'trevor' });
/* expect(json).toEqual({ whatever: 'trevor2' }); */
});
```
`↓ ↓ ↓ ↓ ↓ ↓`
```js
it('counts multiple assertions too', async () => {
expect.hasAssertions();
expect.assertions(1);
const res = await fetch('www.example.com');
// expect(res.json).toBeTruthy();
const json = await res.json();
/*
expect(json).toEqual({ whatever: 'trevor1' });
*/
expect(json).toEqual({ whatever: 'trevor' });
/* expect(json).toEqual({ whatever: 'trevor2' }); */
});
```
### Override
If you add either `expect.assertions(number)` or `expect.hasAssertions()` then your defaults will be favoured and the
plugin will skip the test.
```js
it('will leave test as override supplied', () => {
expect.hasAssertions();
expect.assertions(1);
if (true) {
expect(true).toBe(true);
}
if (false) {
expect(false).toBe(false);
}
});
```
`↓ ↓ ↓ ↓ ↓ ↓`
```js
it('will leave test as override supplied', () => {
expect.hasAssertions();
expect.assertions(1);
if (true) {
expect(true).toBe(true);
}
if (false) {
expect(false).toBe(false);
}
});
```
## Contributors
| [
Matt Phillips](http://mattphillips.io)
[💻](https://github.com/mattphillips/babel-jest-assertions/commits?author=mattphillips "Code") [📖](https://github.com/mattphillips/babel-jest-assertions/commits?author=mattphillips "Documentation") [🚇](#infra-mattphillips "Infrastructure (Hosting, Build-Tools, etc)") [⚠️](https://github.com/mattphillips/babel-jest-assertions/commits?author=mattphillips "Tests") | [
Ramesh Nair](https://hiddentao.com/)
[💻](https://github.com/mattphillips/babel-jest-assertions/commits?author=hiddentao "Code") [📖](https://github.com/mattphillips/babel-jest-assertions/commits?author=hiddentao "Documentation") [💡](#example-hiddentao "Examples") [⚠️](https://github.com/mattphillips/babel-jest-assertions/commits?author=hiddentao "Tests") | [
Huy Nguyen](https://www.huy-nguyen.com/)
[🐛](https://github.com/mattphillips/babel-jest-assertions/issues?q=author%3Ahuy-nguyen "Bug reports") | [
Simon Boudrias](http://simonboudrias.com)
[🐛](https://github.com/mattphillips/babel-jest-assertions/issues?q=author%3ASBoudrias "Bug reports") | [
Giuseppe](http://giuseppe.pizza)
[🤔](#ideas-giuseppeg "Ideas, Planning, & Feedback") |
| :---: | :---: | :---: | :---: | :---: |
## LICENSE
MIT