jest-generator


Testing generators are verbose as they require calling next method of generator each time you want to iterate. jest-generator encapsulates all iteration and assertion logic itself. It provides easy and readable API for testing generator functions.

!Testing with jest-generator

Installation

``bash

yarn add --dev jest-generator

`

or

`bash

npm install --save-dev jest-generator

`

Setup

#### Via setupTestFrameworkScriptFile config

Add jest-generator to your Jest setupTestFrameworkScriptFile configuration

`json
"jest": {
"setupTestFrameworkScriptFile": "jest-generator"
}
`

#### Via setupTest script

Require jest-generator from setupTest script

`js
// ./setupTest.js

require('jest-generator');
`

Then add this config

`json
"jest": {
"setupTestFrameworkScriptFile": "./setupTest.js"
}
`

Usage

`js
// ./pay.js

export default function* pay() {
yield validatePayment();
yield makePayment();

return finishPayment();
}
`

`js
// ./pay.test.js

import pay from './pay';

test('should work correctly', () => {
const iterator = pay();

expect(iterator).toMatchYields([
[validatePayment()],
[makePayment()],
[finishPayment()]
]);
});

`

Usage with other libraries

Usage with Saga


`js
// ./books.js

export function* loadBooks(params) {
try {
const response = yield call(api.loadBooks, params)

yield put(booksLoadedSuccess(response))
} catch (error) {
yield put(booksLoadFail(error.message))
}
}
`

`js
// ./books.test.js

import { loadBooks } from './books';

test('should handle success response', () => {
const params = { id: 201 };
const iterator = loadBooks(params);
const response = [];

expect(iterator).toMatchYields([
[call(api.loadBooks, params), response],
[booksLoadedSuccess(response)],
]);
});

test('should handle error response', () => {
const params = { id: 201 };
const iterator = loadBooks(params);
const response = new Error('failed to load books');

expect(iterator).toMatchYields([
[call(api.loadBooks, params), response],
[put(booksLoadFail(response.message))],
]);
});

`

API

`js
.toMatchYields(
yieldValues: [
[yieldValue: any, returnType?: any | Error]
]
)
`

Matches iterator against given yield values

`js
expect(itetaor).toMatchYields([
[callAPI()]
])
`

In order to return value from yield, simply pass your return value as second array value

`js
function* gen() {
const response = yield fetch()
yield update(response)
}

const mockResponse = {};
const iterator = gen();

expect(iterator).toMatchYields([
[fetch(), mockResponse],
[update(mockResponse)]
])
`

In order to throw error from yield, you should simply pass Error instance to return type

`js
function* gen() {
const response = yield fetch()
yield update(response)
}

const mockErrorResponse = new Error('network error');
const iterator = gen();

expect(iterator).toMatchYields([
[fetch(), mockErrorResponse],
[handleError(mockErrorResponse)]
])
``

Licence

This project is licensed under the MIT License - see the LICENSE file for details