Introduction

jest-mysql-diff can find out changes of database after executing some code. It can be used in test framework like jest.

Install

npm install jest-mysql-diff

How to use

const MysqlDiffer = require('jest-mysql-diff');
const differ = new MysqlDiffer({
  mysql: {
    host: 'your-host',
    user: 'your-user',
    password: 'your-password',
    database: 'your-database'
  }
});

async beforeAllTest() {
  await differ.register('main', 'your-sql-absolute-path');
}

async someTest() {
  await differ.use('main');
  await runSomeCode();
  const changes = await differ.diff();
}

async afterAllTest() {
  await differ.end();
}

Used in Jest

You can create MysqlDiffer object and register some sql files in globalSetup. And then call use in beforeEach to reset database. Use diff to get changes and compare it with snapshot to make sure database changes are expected. Finally, we can call end in globalTeardown to close connecton.

test('some test', async () => {
  await differ.use('main');
  await runSomeCode();
  const changes = await differ.diff();
  expect(changes).toMatchSnapshot();
})

Make it fast

MysqlDiffer will read whole database and make tests become very slow. Running Mysql in memory can speed it up.

In unix system, there is a directory /dev/shm, it works just like normal file system except it keeps data in momery instead of disk. So just set Mysql data directory to it.

API

MysqlDiffer

this library exports a class, constructor accept one parameter options.

const options = {
  mysql: {
    host: 'your-host',
    user: 'your-user',
    password: 'your-password',
    database: 'your-database'
  }
}

const differ = new MysqlDiffer(options);

MysqlDiffer.register

register will execute a sql file and remember how database looks like. First parameter will name the corresponding sql file.

await differ.register('main', 'your-sql-absolute-path');

MysqlDiffer.use

After testing, we could call function use with parameter name to reset database for next test.

await differ.use('main');

MysqlDiffer.diff

diff will compare present database state with the state before testing. diff will return a readable result that can tell us how database is changed.

const changes = await differ.diff()

MysqlDiffer.end

After all tests, you should call end to close database connection.

await differ.end();