问Jest 'spyOn‘TypeScript类而不覆盖其属性和函数
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Stack Overflow用户

提问于 2020-11-30 00:29:56

回答 1查看 614关注 0票数 0

有谁知道我如何在不覆盖所有内容的情况下spyOn整个类(构造函数和所有方法) (Jest 26.6.3)？

目前，我正在尝试SpyOn (不是模拟)我的运行时，我只想检查它是否被敏捷正确地实例化：

import {
  Agile,
  Runtime,
} from "../../src";
jest.mock("../../src");

// ..

const RuntimeMock = Runtime as jest.MockedClass<typeof Runtime>;

// ..

const agile = new Agile();
expect(RuntimeMock).toHaveBeenCalledWith(/* ... */)

// ..

但是Runtime的所有属性函数都被Jest覆盖，因此它根本不被实例化。

是否有一种方法可以获得类似于spyOn方法的行为，但是有一个完整的类，因为我只想检查运行时的构造函数是否在Agile类expect(RuntimeMock).toHaveBeenCalledWith(/* ... */)中被正确调用

也许这是我的导入逻辑中的一个问题，因为我从一个模块internal.ts导入所有类，正因为如此，Jest可能无法正确地重新创建这些类，但我不知道(https://github.com/agile-ts/agile/blob/tests/rewrite-tests/packages/core/src/internal.ts)。

typescript

jestjs

mocking

ts-jest

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回答 1

Stack Overflow用户

发布于 2022-11-30 17:21:45

这是我的解决办法。最后，我创建了这个代码片段，它可以spyOn整个类，包括它的构造函数。而且使用方法也很简单，您可以将这个片段添加到文件中，并在需要时导入它。

这是代码(类型记录/ES6)：

/**
 * spyOn references to classes. Use it with spyOnClass
 */
export const classSpy: any = {};

/**
 * Utility to Spy On all class methods. Not including the constructor
 * @returns a spyOn references to all the class methods
 * includes the methods mockClear and mockReset as convenience
 * to trigger the respective method for all the spies
 */
// eslint-disable-next-line @typescript-eslint/explicit-module-boundary-types
export function spyOnClassMethods(proto: any): any {
    const properties = Object.getOwnPropertyNames(proto);
    const spyHolder: any = {};
    for (const i in properties) { spyHolder[properties[i]] = jest.spyOn(proto, properties[i]); }
    spyHolder.mockClear = (): void => { for (const i in properties) { spyHolder[properties[i]].mockClear(); } };
    spyHolder.mockReset = (): void => { for (const i in properties) { spyHolder[properties[i]].mockReset(); } };
    return spyHolder;
}
// To attend jest.mock problems, the should start with 'mock'
const mocksSpyOnClassMethods = spyOnClassMethods;

/**
 * Utility to Spy On all class methods and its constructor.
 */
// eslint-disable-next-line @typescript-eslint/explicit-module-boundary-types
export function spyOnClass(mockModuleName: string, mockClassName: string): any {
    classSpy[mockClassName] = {};
    jest.mock(mockModuleName, () => {
        const module = jest.requireActual(mockModuleName) as any;
        const mock = {};
        classSpy[mockClassName] = mocksSpyOnClassMethods(module[mockClassName].prototype);
        mock[mockClassName] = jest.fn().mockImplementation(
            (...args: any[]) => {
                const instance = new module[mockClassName](...args);
                classSpy[mockClassName].constructor = mock[mockClassName];
                return instance;
            }
        );
        return { ...module, ...mock };
    });
}

用法示例：

import { classSpy, spyOnClass } from './mock-utils';

// This must come before other imports that use ClassName.
spyOnClass('module-name', 'ClassName');

import { ClassName } from 'module-name';

test('this', () => {
    doSomethingThatUsesClassName();
    expect(classSpy.ClassName.constructor).toHaveBeenCalled();
    expect(classSpy.ClassName.someMethod).toHaveBeenCalled();
});