node.js - 如何使用 Jest 来模拟 Knex

Question

我正在尝试使用 jest 来模拟 knex 以进行以下实现

 const knex = Knex({ client: "mysql"})

    const query = knex("table_name")
      .where({
        title: "xxx-yyy",
        lang: "eng"
      })
      .select()
      .orderBy('date', 'desc')
      .toSQL()
      .toNative()
      

下面我试过了，但是没用，出现错误“TypeError: knex is not a function”

jest.mock("knex", () => {
  return () => {
    return {
      knex: () => {
        where: () => {
          select: () => {
            orderBy: () => {
              toSQL: () => {
                toNative: jest.fn()
              }
            }
          }
        }
      }
    }
  }
})

非常感谢您对此的任何帮助。

Answer 1

jest.mock() 将使用自动模拟版本模拟模块，factory 和 options 是可选的。

您可以使用 mockFn.mockReturnThis()模拟方法链接调用。

另外，如果你在模块范围内初始化Knex，你需要在设置mock之后require模块。

例如

index.js:

import Knex from 'knex';

const knex = Knex({ client: 'mysql' });

export function main() {
  const query = knex('table_name')
    .where({
      title: 'xxx-yyy',
      lang: 'eng',
    })
    .select()
    .orderBy('date', 'desc')
    .toSQL()
    .toNative();
}

index.test.js:

import Knex from 'knex';

jest.mock('knex');

describe('68717941', () => {
  test('should pass', () => {
    const querybuilder = {
      where: jest.fn().mockReturnThis(),
      select: jest.fn().mockReturnThis(),
      orderBy: jest.fn().mockReturnThis(),
      toSQL: jest.fn().mockReturnThis(),
      toNative: jest.fn(),
    };
    const mKnex = jest.fn().mockReturnValue(querybuilder);
    Knex.mockReturnValue(mKnex);
    const { main } = require('./');
    main();
    expect(Knex).toBeCalledWith({ client: 'mysql' });
    expect(mKnex).toBeCalledWith('table_name');
    expect(querybuilder.where).toBeCalledWith({ title: 'xxx-yyy', lang: 'eng' });
    expect(querybuilder.select).toBeCalledTimes(1);
    expect(querybuilder.orderBy).toBeCalledWith('date', 'desc');
    expect(querybuilder.toSQL).toBeCalledTimes(1);
    expect(querybuilder.toNative).toBeCalledTimes(1);
  });
});

测试结果:

 PASS  examples/68717941/index.test.js (8.844 s)
  68717941
    ✓ should pass (7464 ms)

----------|---------|----------|---------|---------|-------------------
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:       1 passed, 1 total
Snapshots:   0 total
Time:        9.439 s