sample_test.js

const withDatabase = require('../utils');


describe('model.getUsers', () => {
  it('returns all users', withDatabase([
    { _table: 'user', id: 1, name: 'User 1' },
    { _table: 'user', id: 1, name: 'User 1' },
  ], async (model) => {
    expect(model.getUsers()).toMatchObject([...]);
  }));
});

describe('model.createUser', () => {
  it('create user', withDatabase([], async (model) => {
    expect(model.createUser('test user')).toMatchObject({ ... })
  }));
});

test_utils.js

const { Client } = require('pg');
const { stripIndent } = require('common-tags');
const model = require('../src/model');


function withDatabase(fixtures, testFun) {
  return async () => {
    const db = new Client({ database: global.TEST_DATABASE_NAME });
    await db.connect();
    await db.query('BEGIN');
    try {
      for (const fixture of fixtures) {
        const fields = Object.keys(fixture).filter((f) => f.charAt(0) !== '_');
        await db.query(stripIndent`
          INSERT INTO ${fixture._table} (${fields.join(', ')})
          VALUES (${fields.map((_, i) => `$${i + 1}`)})
        `, fields.map((f) => fixture[f]));
      }
      await testFun(new Model(db););
    } finally {
      await db.query('ROLLBACK');
      await db.end();
    }
  };
}

module.exports = withDatabase;

example of "asynchronous wrapper" used to set up DB connection with fully isolated transaction for testing purposes.