[英]Mocking require statements with Jest
sum.js
module.exports = function sum(a, b){
return a + b;
};
Thing.js
var sum = require("./sum");
module.exports = class Thing {
add(a, b){
return sum(a, b);
}
}
Thing.test.js
test('1 + 2 = 3', () => {
//Arrange
var Thing = require('./Thing');
var thing = new Thing();
//Act
var result = thing.add(1, 2);
//Assert
expect(result).toBe(3);
});
test('sum mocked', () => {
//Arrange
jest.mock('./sum', () => {
return jest.fn(() => 42);
});
var Thing = require('./Thing');
var thing = new Thing();
//Act
var result = thing.add(1, 2);
//Assert
expect(result).toBe(42);
});
在测试时如何模拟总和'require'依赖? 我收到以下错误。
sum mocked
expect(received).toBe(expected)
Expected value to be (using ===):
42
Received:
3
有趣的是,如果我单独运行每个测试,只有他们自己都可以正常工作。
在过去,我曾使用proxyquire做这样的事情但我想尽可能避免它。
在测试中,我补充道
beforeEach(() => {
jest.resetModules();
});
并且测试按预期通过。
我觉得每个测试文件的模拟工作。 不要问我为什么¯\\ _(ツ)_ /¯
对我来说最好的方法是设置这样的测试:
// sum.test.js
//Arrange
const sum = require('./sum');
test('1 + 2 = 3', () => {
//Act
const result = sum(1, 2);
//Assert
expect(result).toBe(3);
});
和:
// Thing.test.js
//Arrange
const Thing = require('./Thing');
// jest.mock are hoisted so you can keep imports/require on top
const sumSpy = jest.fn(() => 42);
jest.mock('./sum', () => sumSpy);
test('Thing', () => {
const thing = new Thing();
//Act
const result = thing.add(1, 2);
//Assert
expect(sumSpy).toHaveBeenCalledTimes(1);
expect(result).toBe(42);
});
您甚至可以为每个测试提供不同的模拟实现,例如:
sumSpy.mockImplementation(() => NaN);
取自Jest Docs。
beforeEach(() => {
jest.resetModules();
});
test('moduleName 1', () => {
jest.doMock('../moduleName', () => {
return jest.fn(() => 1);
});
const moduleName = require('../moduleName');
expect(moduleName()).toEqual(1);
});
test('moduleName 2', () => {
jest.doMock('../moduleName', () => {
return jest.fn(() => 2);
});
const moduleName = require('../moduleName');
expect(moduleName()).toEqual(2);
});
https://facebook.github.io/jest/docs/en/jest-object.html#jestdomockmodulename-factory-options
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