无法使用jest模拟nodejs中类的实例函数(来自类的新实例的函数)

Question

在component.js中，需要模拟行：

const accessValue = await objValueClass.getValue();

运行component.test.js时，在console.log中，accessValue将作为undefined出现

component.test.js

describe('** Handler unit tests **', () => {
test('test 1', async () => {
const { ValueClass } = require('../../ValueClass');
jest.mock('../../ValueClass');
const objValueClass = new ValueClass();
objValueClass.getValue.mockResolvedValue('abcd');
const { component } = require('../../component');
const res = await component();
});
});

component.js

const { ValueClass } = require('../../ValueClass');

const component = async () => {
const objValueClass = new ValueClass();
const accessValue = await objValueClass.getValue();
console.log('accessValue###', accessValue);
}
module.exports = component;

ValueClass.js

class ValueClass {
async getValue() {
const a = 'a';
const b = 'b';
return a+b;
}
}
module.exports = {
ValueClass
};

Answer 1

这是我的单元测试解决方案：

component.test.js:

const { ValueClass } = require('./ValueClass');
const component = require('./component');
jest.mock('./ValueClass', () => {
const valueClassInstance = {
getValue: jest.fn(),
};
return { ValueClass: jest.fn(() => valueClassInstance) };
});
describe('** Handler unit tests **', () => {
afterAll(() => {
jest.resetAllMocks();
});
test('test 1', async () => {
const objValueClass = new ValueClass();
objValueClass.getValue.mockResolvedValue('abcd');
const res = await component();
expect(objValueClass.getValue).toBeCalledTimes(1);
});
});

单元测试结果：

PASS  src/stackoverflow/65097473/component.test.js (9.297s)
** Handler unit tests **
✓ test 1 (16ms)
console.log src/stackoverflow/65097473/component.js:764
accessValue### abcd
--------------|----------|----------|----------|----------|-------------------|
File          |  % Stmts | % Branch |  % Funcs |  % Lines | Uncovered Line #s |
--------------|----------|----------|----------|----------|-------------------|
All files     |      100 |      100 |      100 |      100 |                   |
component.js |      100 |      100 |      100 |      100 |                   |
--------------|----------|----------|----------|----------|-------------------|
Test Suites: 1 passed, 1 total
Tests:       1 passed, 1 total
Snapshots:   0 total
Time:        10.508s