Jest

Jest ?

Jest est un Framwork fait par Facebook.

Environnement de test

jest

yarn add jest

@types/jest

yarn add @types/jest

1er Test

sum.js

const sum = (a,b) => a+b;

sum.test.js

const sum = require("./sum");

test("1 + 2 = 3", () => {
  expect(sum(1, 2)).toBe(3);
});

package.json

ajouter "scripts"comme cela :

{
  "name": "jest",
  "version": "1.0.0",
  "main": "index.js",
  "license": "MIT",
  "dependencies": {
    "@types/jest": "^26.0.23",
    "jest": "^26.6.3"
  },
  "scripts" :{
    "test":"jest --watchAll verbose"
  }
}

yarn test

$yarn test

PASS ./sum.test.js
✓ 1 + 2 = 3 (3 ms)

Test Suites: 1 passed, 1 total

Tests: 1 passed, 1 total
Snapshots: 0 total
Time: 1.9 s
Ran all test suites.
Watch Usage: Press w to show more.

test === it

const sum = require("./sum");

//it() === test()
it("1 + 2 = 3", () => {
  expect(sum(1, 2)).toBe(3);
});

Describe

describe("", () =>{});

describe("sum test", () => {
 it("1 + 2 == 3", () => {
   expect(sum(1, 2)).toBe(3);
 });
 it("calculate all numbers in array", () => {
   expect(sumOf([1, 2, 3, 4, 5, 6, 7, 8, 9, 10])).toBe(55);
 });
});

Refectoring

Reformer la function sumOf avec .reduce()
cf/array.reduce([callback], [initial_value])

callback = (accumulator, currentValue) => accumulator + currentValue

sum.js

const sum = (a, b) => a + b;
const sumOf = (numbers) => {
  return numbers.reduce((acc, current) => acc + current, 0);
};

exports.sum = sum;
exports.sumOf = sumOf;

Conclusion

test === it

describe() est servi pour diviser, grouper les tests.