如何 jest.mock "git-simple"分支本地函数？

Question

我使用simple-git包。我有以下功能：

import simpleGit from 'simple-git';
/**
* The function returns the ticket Id, is presents, in the branch name
* @returns ticket Id
*/
export const getTicketIdFromBranchName = async (ticketRegex: RegExp) => {
const git = simpleGit();
try {
const localBranches = await git.branchLocal();
const currentBranch = localBranches.current;
const currentBranchTicketMatches = currentBranch.match(ticketRegex);
if (currentBranchTicketMatches) {
return currentBranchTicketMatches[0];
}
return null;
} catch {
return null;
}
};

我尝试为这个函数创建一个单元测试：

import { getTicketIdFromBranchName } from '@/utils/git-info';
const TICKET_ID_REGEX = /((?<!([A-Z]{1,10})-?)[A-Z]+-d+)/.source;
describe('[utils/git-info]', () => {
it('getTicketIdFromBranchName | Function should proper ticket Id when there is one', async () => {
const ticketId = 'CLO-1234';
jest.mock('simple-git', () => {
const mGit = {
branchLocal: jest.fn(() => Promise.resolve({ current: `${ticketId} DUMMY TEST` })),
};
return jest.fn(() => mGit);
});
const result = await getTicketIdFromBranchName(new RegExp(TICKET_ID_REGEX));
expect(result === ticketId).toEqual(true);
});
});

但是单元测试失败了。我说我希望得到true但它在最后一行中得到了false。

我想我以错误的方式使用jest.mock。

Answer 1

官方文档对jest.mock的使用进行了关键描述。

注意：为了正确模拟，Jest 需要jest.mock('moduleName')与require/import语句处于同一范围内。

在测试用例函数作用域内调用jest.mock('moduleName')，但在模块作用域中importgit-info模块。这就是为什么模拟不起作用的原因。

在测试用例函数中使用require('moduleName')或await import('moduleName')。require/import和jest.mock()语句的顺序无关紧要。

git-info.js：

import simpleGit from 'simple-git';
/**
* The function returns the ticket Id, is presents, in the branch name
* @returns ticket Id
*/
export const getTicketIdFromBranchName = async (ticketRegex) => {
const git = simpleGit();
try {
const localBranches = await git.branchLocal();
const currentBranch = localBranches.current;
const currentBranchTicketMatches = currentBranch.match(ticketRegex);
if (currentBranchTicketMatches) {
return currentBranchTicketMatches[0];
}
return null;
} catch {
return null;
}
};

git-info.test.js：

const TICKET_ID_REGEX = /((?<!([A-Z]{1,10})-?)[A-Z]+-d+)/.source;
describe('[utils/git-info]', () => {
it('getTicketIdFromBranchName | Function should proper ticket Id when there is one', async () => {
const { getTicketIdFromBranchName } = await import('./git-info');
const ticketId = 'CLO-1234';
jest.mock(
'simple-git',
() => {
const mGit = {
branchLocal: jest.fn(() => Promise.resolve({ current: `${ticketId} DUMMY TEST` })),
};
return jest.fn(() => mGit);
},
{ virtual: true }
);
const result = await getTicketIdFromBranchName(new RegExp(TICKET_ID_REGEX));
expect(result === ticketId).toEqual(true);
});
});

测试结果：

PASS  stackoverflow/71808909/git-info.test.js (7.439 s)
[utils/git-info]
✓ getTicketIdFromBranchName | Function should proper ticket Id when there is one (6892 ms)
-------------|---------|----------|---------|---------|-------------------
File         | % Stmts | % Branch | % Funcs | % Lines | Uncovered Line #s 
-------------|---------|----------|---------|---------|-------------------
All files    |   84.62 |       50 |     100 |   81.82 |                   
git-info.js |   84.62 |       50 |     100 |   81.82 | 19-21             
-------------|---------|----------|---------|---------|-------------------
Test Suites: 1 passed, 1 total
Tests:       1 passed, 1 total
Snapshots:   0 total
Time:        8.215 s, estimated 9 s

软件包版本："jest": "^26.6.3"