knex-mock-client

A mock client for Knex which allows you to write unit tests with DB interactions with a breeze.

Installation

To use this lib, first you will have to install it:

npm i --save-dev knex-mock-client

or

yarn add --dev knex-mock-client

Example

Mocking an insert statement

// my-cool-controller.ts
import { db } from '../common/db-setup';

export async function addUser(user: User): Promise<{ id }> {
  const [insertId] = await db.insert(user).into('users');

  return { id: insertId };
}

// my-cool-controller.spec.ts
import { expect } from '@jest/globals';
import { createTracker, MockClient } from 'knex-mock-client';
import { faker } from '@faker-js/faker';
import { db } from '../common/db-setup';

jest.mock('../common/db-setup', () => {
   const knex = require('knex');
   return {
      db: knex({ client: MockClient }),
   };
});

describe('my-cool-controller tests', () => {
   let tracker: Tracker;

   beforeAll(() => {
      tracker = createTracker(db);
   });

   afterEach(() => {
      tracker.reset();
   });

   it('should add new user', async () => {
      const insertId = faker.number.int();
      tracker.on.insert('users').response([insertId]);

      const newUser = { name: 'foo bar', email: 'test@test.com' };
      const data = await addUser(newUser);

      expect(data.id).toEqual(insertId);

      const insertHistory = tracker.history.insert;

      expect(insertHistory).toHaveLength(1);
      expect(insertHistory[0].method).toEqual('insert');
      expect(insertHistory[0].bindings).toEqual([newUser.name, newUser.email]);
   });
});

Each one of on methods (select, insert,update, delete, any) are accepting a query matcher.
There are 3 kind of matchers:

1. String - will match part of the given sql using String.includes

   tracker.on.select('select * from users where `id`=?').response([]);

2. RegEx - will match the given sql with the given regex

   tracker.on.update(/update users where .*/).response([]);

3. Function - you can specify a custom matcher by providing a function.
   This function will accept RawQuery as an argument and should return a boolean value.

   tracker.on
     .insert(
       ({ method, sql, bindings }: RawQuery) =>
         method === 'insert' && /^insert into `users`/.test(sql) && bindings.includes('secret-token')
     )
     .response([]);

Query handlers

You can specify the db response by calling:

1. response<T = any>(data: T | ((rawQuery: RawQuery) => (T | Promise<T>))) - This will register a permanent query handler.

   If a value is provided, it will be returned directly. If a callback is passed, it will be called with the RawQuery and should return a value for the tracker to return.

   tracker.on.select('select * from users where `id`=?').response([{ id: 1, name: 'foo' }]);

   tracker.on
     .select('select * from users where `id`=?')
     .response((rawQuery) => [{ id: 1, name: 'foo' }]);

2. responseOnce<T = any>(data: T | ((rawQuery: RawQuery) => (T | Promise<T>)))- This will register a one-time query handler, which will be removed from handlers list after the first usage.

   If a value is provided, it will be returned directly. If a callback is passed, it will be called with the RawQuery and should return a value for the tracker to return.

   tracker.on.select('select * from users where `id`=?').responseOnce([{ id: 1, name: 'foo' }]);

   tracker.on
     .select('select * from users where `id`=?')
     .responseOnce((rawQuery) => Promise.resolve([{ id: 1, name: 'foo' }]));

3. simulateError(errorMessage: string) - will register a permanent failure handler for the matched query

   tracker.on.select('select * from users where `id`=?').simulateError('Connection lost');

4. simulateErrorOnce(errorMessage: string) - will register a one-time failure handler, after the first usage it will be removed from handlers list.

   tracker.on.select('select * from users where `id`=?').simulateErrorOnce('Connection lost');

You can reset handlers by calling tracker.resetHandlers() which will remove all handlers for all query methods.

History Calls

Each db request that your app makes throughout knex will be registered in a scoped (by query method) history call list. It will also be registered in tracker.history.all.

Each call is an object with the interface of RawQuery.

interface RawQuery {
  method: 'select' | 'insert' | 'update' | 'delete';
  sql: string;
  bindings: any[];
  options: Record<string, any>;
  timeout: boolean;
  cancelOnTimeout: boolean;
  __knexQueryUid: string;
  queryContext: any;
}

Specific dialects

Some DB's (like postgress) has specific dialects, for the mockClient build the proper query you must pass the dialect property.

db = knex({
  client: MockClient,
  dialect: 'pg', // can be any Knex valid dialect name.
});

const givenData = [{ id: faker.number.int() }];
tracker.on.select('table_name').response(givenData);

const data = await db('table_name').distinctOn('age');

You can reset all history calls by calling tracker.resetHistory().

You can reset queryHandlers & history by calling tracker.reset().

This lib got inspiration from axios-mock-adapter api️.