README.md

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We use database to persist data. While running tests, we might insert or delete rows from the database. So it is a common practise to use a separate database for the purpose of testing. By doing this, we can easily create or destroy tables with peace of mind.

If we check the config.json file generated by sequelize-cli, it already has a configuration assigned to test. We will modify npm scripts to use this configuration for running tests.

First, we add a npm script in package.json to create the database for test purposes.

"scripts": {
    "db:create:test": "NODE_ENV=test npx sequelize-cli db:create",
    "test": "jest --detectOpenHandles",
    "prepare": "husky install"
  },

Then we will add a script pretest which will run before running test script. Here we will delete the existing database from previous run as we need clean slate before each test run.

"scripts": {
    "db:create:test": "NODE_ENV=test npx sequelize-cli db:create",
    "pretest": "NODE_ENV=test npx sequelize-cli db:drop && NODE_ENV=test npx sequelize-cli db:create",
    "test": "jest --detectOpenHandles",
    "prepare": "husky install"
  },

And finally modify the test script to use the test database configuration.

"scripts": {
    "db:create:test": "NODE_ENV=test npx sequelize-cli db:create",
    "pretest": "NODE_ENV=test npx sequelize-cli db:drop && NODE_ENV=test npx sequelize-cli db:create",
    "test": "NODE_ENV=test jest --detectOpenHandles",
    "prepare": "husky install"
  },

Now, we can execute the scripts to create test database.

npm run db:create:test

You should see an output like the following:

> wd201@1.0.0 db:create:test
> NODE_ENV=test npx sequelize-cli db:create


Sequelize CLI [Node: 16.17.0, CLI: 6.4.1, ORM: 6.21.4]

Loaded configuration file "config/config.json".
Using environment "test".
Database todo_db_test created.

Now, we need to modify our tests to use the newly generated models. Edit __tests__/todo.js with following content. We will create the tables before running each tests.

// __tests__/todo.js
/* eslint-disable no-undef */
const db = require("../models");

describe("Todolist Test Suite", () => {
  beforeAll(async () => {
    await db.sequelize.sync({ force: true });
  });

  test("Should add new todo", async () => {
    const todoItemsCount = await db.Todo.count();
    await db.Todo.addTask({
      title: "Test todo",
      completed: false,
      dueDate: new Date(),
    });
    const newTodoItemsCount = await db.Todo.count();
    expect(newTodoItemsCount).toBe(todoItemsCount + 1);
  });
});

And your models/todo.js should look like:

// models/todo.js
'use strict';
const {
  Model
} = require('sequelize');
module.exports = (sequelize, DataTypes) => {
  class Todo extends Model {
    /**
     * Helper method for defining associations.
     * This method is not a part of Sequelize lifecycle.
     * The `models/index` file will call this method automatically.
     */
     static async addTask(params) {
      return  await Todo.create(params);
    }
    static associate(models) {
      // define association here
    }
    displayableString() {
      let checkbox = this.completed ? "[x]" : "[ ]";
      return `${this.id}. ${checkbox} ${this.title} ${this.dueDate}`;
    }
  }
  Todo.init({
    title: DataTypes.STRING,
    dueDate: DataTypes.DATEONLY,
    completed: DataTypes.BOOLEAN
  }, {
    sequelize,
    modelName: 'Todo',
  });
  return Todo;
};

Next we can run the tests and it would use the credentials for test database.

npm test

You should see the tests getting executed and producing an output like the following:

 PASS  __tests__/todo.js
  Todolist Test Suite
    ✓ Should add new todo (40 ms)

Test Suites: 1 passed, 1 total
Tests:       1 passed, 1 total
Snapshots:   0 total
Time:        0.974 s, estimated 2 s
Ran all test suites.

Conclusion

In this lesson, we have learned how to configure and use a separate database for testing purposes.