Jest使用
使用流程
Jest 解析
-
匹配器
toBe使用 Object.is来进行精准匹配的测试
test(‘two plus two is four’, () => {
expect(2 + 2).toBe(4);
});
-
toEqual 递归检查对象或数组的每个字段。
test(‘对象赋值’, () => {
const data = {one: 1};
data[‘two’] = 2;
expect(data).toEqual({one: 1, two: 2});
});
-
可以使用与匹配相反的 not 来进行测试
test(‘adding positive numbers is not zero’, () => {
for (let a = 1; a < 10; a++) {
for (let b = 1; b < 10; b++) {
expect(a + b).not.toBe(0);
}
}
});
-
真值
代码中的undefined, null, and false有不同含义,若你在测试时不想区分他们,可以用真值判断。 Jest提供helpers供你使用。
toBeNull 只匹配 null
toBeUndefined 只匹配 undefined
toBeDefined 与 toBeUndefined 相反
toBeTruthy 匹配任何 if 语句为真
toBeFalsy 匹配任何 if 语句为假
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数字
大多数的比较数字有等价的匹配器。
test(‘two plus two’, () => {
const value = 2 + 2;
expect(value).toBeGreaterThan(3);
expect(value).toBeGreaterThanOrEqual(3.5);
expect(value).toBeLessThan(5);
expect(value).toBeLessThanOrEqual(4.5);
// toBe and toEqual are equivalent for numbers
expect(value).toBe(4);
expect(value).toEqual(4);
});
-
对于比较浮点数相等,使用 toBeCloseTo 而不是 toEqual,因为你不希望测试取决于一个小小的舍入误差。
test(‘两个浮点数字相加’, () => {
const value = 0.1 + 0.2;
//expect(value).toBe(0.3); 这句会报错,因为浮点数有舍入误差
expect(value).toBeCloseTo(0.3); // 这句可以运行
});
});
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字符串
您可以检查对具有 toMatch 正则表达式的字符串︰
test(‘there is no I in team’, () => {
expect(‘team’).not.toMatch(/I/);
});
test(‘but there is a “stop” in Christoph’, () => {
expect(‘Christoph’).toMatch(/stop/);
});
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数组和可迭代对象
你可以通过 toContain来检查一个数组或可迭代对象是否包含某个特定项:
const shoppingList = [
‘diapers’,
‘kleenex’,
‘trash bags’,
‘paper towels’,
‘milk’,
];
test(‘shoppingList数组中包含milk’, () => {
expect(shoppingList).toContain(‘milk’);
expect(new Set(shoppingList)).toContain(‘milk’);
});
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例外
若你想测试某函数在调用时是否抛出了错误,你需要使用 toThrow。
function compileAndroidCode() {
throw new Error(‘you are using the wrong JDK!’);
}
test('compiling android goes as expected', () => {
expect(() => compileAndroidCode()).toThrow();
expect(() => compileAndroidCode()).toThrow(Error);
// You can also use a string that must be contained in the error message or a regexp
expect(() => compileAndroidCode()).toThrow('you are using the wrong JDK');
expect(() => compileAndroidCode()).toThrow(/JDK/);
// Or you can match an exact error message using a regexp like below
expect(() => compileAndroidCode()).toThrow(/^you are using the wrong JDK$/); // Test fails
expect(() => compileAndroidCode()).toThrow(/^you are using the wrong JDK!$/); // Test pass
});
code
-
jest.config.js
/** @type {import('ts-jest').JestConfigWithTsJest} */
module.exports = {
preset: 'ts-jest',
testEnvironment: 'node',
testMatch: [
// glob 格式
// '**/__tests__/**/*.[jt]s?(x)',
'**/__test__/**/*.[jt]s?(x)',//指定文件夹,其他tests文件夹不测试
// '**/?(*.)+(spec|test).[jt]s?(x)',
],
// 正则表达式格式,与 testMatch 互斥,不能同时声明
// testRegex: '(/__tests__/.*|(\\.|/)(test|spec))\\.[jt]sx?$',
};
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utils/index.tsx
export function toDigit(num): string {
if (!num) {
return '-';
}
const numArr = (`${num}`).split('.');
num = numArr[0];
let result = '';
while (num.length > 3) {
result = `,${num.slice(-3)}${result}`;
num = num.slice(0, num.length - 3);
}
if (num) {
result = num + result;
}
if (numArr.length === 1) {
return `${result}.00`;
} else if (numArr[1].length === 2) {
return `${result}.${numArr[1]}`;
} else {
return `${result}.${numArr[1]}0`;
}
}
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__test__/toDigit.test.ts
import { describe, test, expect } from '@jest/globals';
import { toDigit } from '../src/utils/index';
const arr: number[] = [2344513099.66, 53450000, 0];
describe('utils toDigit test', () => {
test('toDigit test 1', () => {
expect(toDigit(arr[0])).toBe('2,344,513,099.66');
});
test('toDigit test 2', () => {
expect(toDigit(arr[1])).toBe('53,450,000.00');
});
test('toDigit test 3', () => {
expect(toDigit(arr[2])).toBe('-');
});
});