jest-random-mock

> Mock Math.random when run unit test cases with jest, output deterministic random number.


Install

This should only be installed as a development dependency (devDependencies) as it is only designed for testing.

``bash
$ npm i --save-dev jest-random-mock
`

Usage

> Use the only 3 api for test cases.

- mock(): Mocks the Math.random, with deterministic random function.
- clear(): Shut down the mock system, use original Math.random.
- createDeterministicRandom(): Return a deterministic random number generator.

Use it in jest env.

`js
import { mock, clear } from "jest-random-mock";

beforeEach(() => {
mock();
});

test("your test cases", () => {
mock();
const r1 = Math.random();
clear();

mock();
const r2 = Math.random();
clear();

// expect r1 should be same with r2.
});

afterEach(() => {
clear();
});
`

Use it as a library.

`ts
import { createDeterministicRandom } from "jest-random-mock";

const random = createDeterministicRandom();

const v1 = random();
const v2 = random();
`

Random distribution

!image

`ts
import { Chart } from "@antv/g2";
import { createDeterministicRandom } from "jest-random-mock";

const random = createDeterministicRandom();

const chart = new Chart({
container: "container",
autoFit: true,
theme: "academy",
});

const flex = chart
.spaceFlex()
.attr("direction", "row")
.attr("ratio", [1, 1, 1]);

const TIMES = [100, 1000, 10000];

TIMES.forEach((time) => {
const data = new Array(time).fill(0).map(() => ({ v: random() }));
flex
.rect()
.data(data)
.encode("x", "v")
.encode("color", "steelblue")
.transform({ type: "binX", y: "count", thresholds: 10 })
.style("inset", 0.5)
.axis("x", { title: false })
.axis("y", { title: ${time} times Radnom });
});

chart.render();
``

License

MIT@hustcc.