[英]How to test async await pg connection with jest?
我正在嘗試使用async/await
測試一個與 pg 建立連接的函數,
import pg from 'pg';
module.exports.test = async (event, context, callback) => {
const client = new pg.Client(someConnectionString);
try {
await client.connect();
} catch (e) {
return callback(e);
}
try {
await client.query(await someAsyncFunction(test));
client.end();
return callback(null, 'success');
} catch (e) {
client.end();
return callback(e);
}
};
真的不明白我將如何用玩笑來嘲笑這個? 有什么想法嗎?
首先,開玩笑,你可以返回一個測試異步代碼的承諾:
import pg from 'pg';
module.exports.test = async (event, context) => {
const client = new pg.Client(someConnectionString);
try {
await client.connect();
await client.query(await someAsyncFunction(test));
} finally {
client.end();
}
};
由於任何async
函數都會返回一個承諾,因此您不必手動處理將錯誤傳遞給回調。
現在關於如何模擬 pg 的問題,您可以創建一個假 pg 對象,但這很少是理想的,我將僅展示一個示例來回答實際問題。
您應該在運行測試之前嘗試設置一個測試數據庫,然后在之后對其進行清理,這樣您就不必模擬任何內容並且可以使用真正的pg
這將大大提高測試的質量。
// mock example:
class MockClient {
async connect() {
}
async query() {
}
}
這是單元測試解決方案:
index.js
:
import pg from 'pg';
import { someAsyncFunction } from './someAsyncFunction';
const someConnectionString = 'someConnectionString';
const test = 'test';
module.exports = async (event, context, callback) => {
const client = new pg.Client(someConnectionString);
try {
await client.connect();
} catch (e) {
return callback(e);
}
try {
await client.query(await someAsyncFunction(test));
client.end();
return callback(null, 'success');
} catch (e) {
client.end();
return callback(e);
}
};
someAsyncFunction.js
:
export async function someAsyncFunction() {}
index.test.js
:
import pg from 'pg';
import fn from './';
import { someAsyncFunction } from './someAsyncFunction';
jest.mock('./someAsyncFunction', () => {
return { someAsyncFunction: jest.fn() };
});
jest.mock('pg', () => {
const mClient = { connect: jest.fn(), query: jest.fn(), end: jest.fn() };
return { Client: jest.fn(() => mClient) };
});
describe('46152048', () => {
afterEach(() => {
jest.clearAllMocks();
});
afterAll(() => {
jest.resetAllMocks();
});
it('should query success', async (done) => {
someAsyncFunction.mockResolvedValueOnce('select 1;');
const mClient = new pg.Client();
mClient.connect.mockResolvedValueOnce();
await fn({}, {}, (err, result) => {
expect(pg.Client).toBeCalledWith('someConnectionString');
expect(someAsyncFunction).toBeCalledWith('test');
expect(mClient.query).toBeCalledWith('select 1;');
expect(mClient.end).toBeCalledTimes(1);
expect(err).toBeNull();
expect(result).toBe('success');
done();
});
});
it('should handle error if connect database failed', async () => {
const mError = new Error('network');
const mClient = new pg.Client();
mClient.connect.mockRejectedValueOnce(mError);
await fn({}, {}, (err, result) => {
expect(err.message).toBe('network');
expect(result).toBeUndefined();
});
});
it('should handle error if query failed', async () => {
const mError = new Error('network');
const mClient = new pg.Client();
mClient.connect.mockResolvedValueOnce();
mClient.query.mockRejectedValueOnce(mError);
await fn({}, {}, (err, result) => {
expect(err.message).toBe('network');
expect(mClient.end).toBeCalledTimes(1);
expect(result).toBeUndefined();
});
});
});
帶有覆蓋率報告的單元測試結果:
PASS src/stackoverflow/46152048/index.test.js
46152048
✓ should query success (11ms)
✓ should handle error if connect database failed (1ms)
✓ should handle error if query failed (1ms)
----------|----------|----------|----------|----------|-------------------|
File | % Stmts | % Branch | % Funcs | % Lines | Uncovered Line #s |
----------|----------|----------|----------|----------|-------------------|
All files | 100 | 100 | 100 | 100 | |
index.js | 100 | 100 | 100 | 100 | |
----------|----------|----------|----------|----------|-------------------|
Test Suites: 1 passed, 1 total
Tests: 3 passed, 3 total
Snapshots: 0 total
Time: 4.103s, estimated 10s
源代碼: https : //github.com/mrdulin/jest-codelab/tree/master/src/stackoverflow/46152048
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