使用笑话进行单元测试时如何模拟普通对象的依赖关系？

Question

在测试ReactJs助手时，我找不到模拟对象导入的方法。所有的例子都展示了如何模拟导入的函数，而没有人谈论模拟导入的对象。

我想模拟的这个基本帮助对象：

filters-state.helper.ts:

export const FiltersStateHelper = {
toggleFilters: <T extends FiltersState>(state: T): T => ({
...state,
isOpen: !state.isOpen
})
};

我正在测试的状态助手中使用它：

search-view-state.helper.ts:

import { FiltersStateHelper } from 'shared/filters/helpers/filters-state.helper';
export const SearchViewStateHelper = {
toggleFilters: <T extends SearchViewState>(state: T): T => ({
...state,
filters: FiltersStateHelper.toggleFilters(state.filters)
})
//... more methods
};

在测试中，嘲讽依赖性失败了，可能是因为我的助手的依赖性在我说嘲笑什么之前就已经解决了：

search-view-state.helper.spec.ts:

import { SearchViewStateHelper as helper } from 'shared/search-view/helpers/search-view-state.helper';
describe('toggleFilters method', () => {
const spy = jest.fn();
jest.doMock('shared/filters/helpers/filters-state.helper', () => {
return {
toggleFilters: spy
};
});
const state = {};
it('should toggle filters', () => {
helper.toggleFilters(state);
expect(spy).toHaveBeenCalled();
});
});

Answer 1

您可以使用jest.spyOn(object，methodName，accessType？(监视FiltersStateHelper对象的toggleFilters方法。

例如

filters-state.helper.ts:

type FiltersState = any;
export const FiltersStateHelper = {
toggleFilters: <T extends FiltersState>(state: T): T => ({
...state,
isOpen: !state.isOpen
})
};

search-view-state.helper.ts:

import { FiltersStateHelper } from './filters-state.helper';
type SearchViewState = any;
export const SearchViewStateHelper = {
toggleFilters: <T extends SearchViewState>(state: T): T => ({
...state,
filters: FiltersStateHelper.toggleFilters(state.filters)
})
// ... more methods
};

search-view-state.helper.spec.ts:

import { SearchViewStateHelper as helper } from './search-view-state.helper';
import { FiltersStateHelper } from './filters-state.helper';
describe('toggleFilters method', () => {
const state = { filters: { isOpen: false } };
it('should toggle filters', () => {
const spy = jest.spyOn(FiltersStateHelper, 'toggleFilters');
helper.toggleFilters(state);
expect(spy).toHaveBeenCalled();
expect(spy).toBeCalledWith({ isOpen: false });
});
});

100%覆盖率的单元测试结果：

PASS  src/stackoverflow/58746881/search-view-state.helper.spec.ts
toggleFilters method
✓ should toggle filters (6ms)
-----------------------------|----------|----------|----------|----------|-------------------|
File                         |  % Stmts | % Branch |  % Funcs |  % Lines | Uncovered Line #s |
-----------------------------|----------|----------|----------|----------|-------------------|
All files                    |      100 |      100 |      100 |      100 |                   |
filters-state.helper.ts     |      100 |      100 |      100 |      100 |                   |
search-view-state.helper.ts |      100 |      100 |      100 |      100 |                   |
-----------------------------|----------|----------|----------|----------|-------------------|
Test Suites: 1 passed, 1 total
Tests:       1 passed, 1 total
Snapshots:   0 total
Time:        3.833s, estimated 8s

源代码：https://github.com/mrdulin/jest-codelab/tree/master/src/stackoverflow/58746881