开玩笑-如何模拟模块使用的类? [英] Jest - how to mock a Class used by a module?
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问题描述
我有一堂课:
class RequestTimeout {
constructor(timeoutMilliseconds) {
this.timeoutMilliseconds = timeoutMilliseconds;
this.timeoutID = undefined;
}
start() {
return new Promise((resolve, reject) => {
this.timeoutID = setTimeout(() => reject(new Error(`Request attempt exceeded timeout of ${this.timeoutMilliseconds}`)), this.timeoutMilliseconds);
});
}
clear() {
if (this.timeoutID) clearTimeout(this.timeoutID);
}
}
module.exports = RequestTimeout;
此类在模块中使用:
const RequestTimeout = require('./request-timeout');
function Request() {
...
async function withTimeout(request, ms) {
const timeout = new RequestTimeout(ms);
return Promise.race([
request(),
timeout.start(),
])
.then(
response => {
timeout.clear();
return response;
},
err => {
timeout.clear();
throw err;
}
);
}
...
}
如何在使用Request
的测试中模拟RequestTimeout
?例如:
How do i mock RequestTimeout
in a test using Request
? For example:
it('should clear the timeout following a successful response', async () => {
nock('http://example.com')
.get('/')
.reply(200, { example: true });
const response = await request.get({ ...baseOptions });
expect(response.example).toEqual(true);
});
推荐答案
//MOCK
let mockGetTimeOutId = jest.fn();
jest.mock('../request-timeout', () => {
return jest.fn().mockImplementation((ms) => {
let timeoutId = undefined;
return {
start: () => new Promise((resolve, reject) => {
timeoutId = setTimeout(() => reject(), ms);
}),
clear: () => mockGetTimeOutId(timeoutId),
}
})
});
//测试
it('should clear the timeout following a successful response', async () => {
nock('http://example.com')
.get('/')
.reply(200, { example: true });
expect(mockGetTimeOutId).toHaveBeenCalledTimes(0);
const response = await request.get({ ...baseOptions });
expect(mockGetTimeOutId).toHaveBeenCalledTimes(1);
expect(response.example).toEqual(true);
});
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