Node.js Specific test-driven improvement with Jest

Check-driven improvement, or TDD, is a reasonably frequent fashion of programming within the office, and, in lots of cases, is necessary for sure initiatives. Fortunately, TDD is fairly easy if you perceive the basics behind the method.

There are additionally many libraries and frameworks used for backend testing in JavaScript. Two of the preferred ones are Jest and Mocha, with options of Jasmine, Ava, Tape, and QUnit.

Node.js now has its personal inbuilt take a look at runner that’s been secure since v18. Nevertheless, it’s nonetheless in experimental mode, so it’s more likely to change over time.

On this article, we’ll talk about the way to use the brand new Node.js take a look at runner for some primary testing, in addition to utilizing Jest for testing totally different endpoints.

Testing on the backend

First, let’s bounce into testing on the backend utilizing Node.js.

Utilizing the Node.js take a look at runner to check backend code

If you wish to use the inbuilt Node.js take a look at runner, it’s good to import the library beneath and comply with the Node.js documentation for operating the assessments:

// JavaScript ESM Modules syntax
import take a look at from 'node:take a look at';

// JavaScript CommonJS syntax
const take a look at = require('node:take a look at');

In fact, you additionally must just be sure you are utilizing v18 or later. You’ll be able to verify which model you’re at present operating within the command line utilizing node -v.

Firstly, let’s see what it’s love to do testing utilizing the in-built Node.js take a look at runner.

Challenge setup

Open your BASH utility and cd to the listing of your alternative. Run the instructions beneath to scaffold your venture:

mkdir node-backend-testing
cd node-backend-testing
npm init -y
contact index.js index.take a look at.js

Subsequent, open the newly created venture in your code editor and add the code to the information they relate to.

Under is the code for the file index.js:

const calcAge = (dob) => {
    const digits = {
        12 months: 'numeric',
    };

    const 12 months = new Date().toLocaleDateString('en-US', digits);

    console.log(12 months);

    return 12 months - dob;
};

const createBox = (x, y) => {
    return x * y;
};

const canDrive = () => {
    const age = 18;

    if (age >= 18) {
        return 'Full Driving Licence';
    } else {
        return 'Provisional License';
    }
};

const powerLevel = () => {
    const energy = 9001;

    if (energy > 9000) {
        return true;
    } else {
        return false;
    }
};

const workSchedule = (employeeOne, employeeTwo) => {
    return employeeOne + employeeTwo;
};

module.exports = {
    calcAge,

    createBox,

    canDrive,

    powerLevel,

    workSchedule,
};

Subsequent, we’ve the code for index.take a look at.js:

const take a look at = require('node:take a look at');

const assert = require('assert/strict');

const {
  calcAge,
  createBox,
  canDrive,
  powerLevel,
  workSchedule,
} = require('./index');

// Calculates how previous somebody is and relying on the 12 months this take a look at may move or fail

take a look at('calculates age', () => {
  return assert.equal(calcAge(2000), 22);
});

// Creates a field with an equal peak and width

take a look at('creates a field', async (t) => {
  await t.take a look at('creates a small field', () => {
    assert.equal(createBox(10, 10), 100);
  });

  await t.take a look at('creates a big field', () => {
    assert.equal(createBox(50, 50), 2500);
  });
});

// Checks to see whether or not or not the particular person has a full driving licence

take a look at('checks license', () => {
  return assert.match(`${canDrive()}`, /Full Driving Licence/);
});

// Confirms that the particular person has an influence stage that's over 9000!

take a look at('confirms energy stage', () => {
  return assert.okay(powerLevel());
});

// Checks to see if the workers have the identical quantity of shift work days in every week

take a look at('staff have an equal variety of work days', () => {
  const employeeOne = ['Monday', 'Tuesday', 'Wednesday,', 'Thursday'];

  const employeeTwo = ['Friday', 'Saturday', 'Sunday,', 'Monday'];

  return assert.equal(workSchedule(employeeOne.size, employeeTwo.size), 8);
});

Lastly, add this run script for the file bundle.json:

"scripts": {

"take a look at": "node index.take a look at.js"

},

The take a look at script runs the Node take a look at runner, which is able to then run the assessments in index.take a look at.js.

Working Node assessments

You’ll solely must run one command from inside the foundation folder. As soon as once more, it’s good to be utilizing Node v18 or later for this to work.

Run the command beneath and it is best to see 5 assessments passing within the console:

npm run take a look at

You’ll be able to mess around with the code inside the index.js and index.take a look at.js information to see the assessments move and fail. If you happen to take a look at the take a look at errors within the console you’ll know what’s failing why.

Let me provide you with some examples beneath.

Calculate age take a look at

To calculate a consumer’s age, use the present 12 months minus their 12 months of delivery. See the instance beneath within the index.take a look at.js file:

take a look at('calculates age', () => {
  return assert.equal(calcAge(2000), 21);
});

To see the take a look at fail, enter an incorrect age like 21. The operate is anticipating a return worth of 22 on this instance, so the quantity 21 makes the take a look at fail.

Create a field take a look at

This take a look at is anticipating solutions of 100 and 2500 for the equations 10 x 10 and 50 x 50, respectively. Enter in values that don’t add as much as the right output to see the take a look at fail.

take a look at('creates a field', async (t) => {
  await t.take a look at('creates a small field', () => {
    assert.equal(createBox(10, 30), 100);
  });

  await t.take a look at('creates a big field', () => {
    assert.equal(createBox(50, 20), 2500);
  });
});

Verify license take a look at

This take a look at checks to see if an individual has a legitimate driver’s licence. Change the age within the index.js file’s canDrive operate to a worth lower than 18. The take a look at will fail.

const canDrive = () => {
  const age = 17;

  if (age >= 18) {
    return 'Full Driving Licence';
  } else {
    return 'Provisional License';
  }
};

Affirm energy stage take a look at

This take a look at checks to see if an individual has an influence stage that over 9000 (did you catch the Dragon Ball Z reference? 😁)

Change the ability stage inside the index.js file’s powerLevel operate to lower than 9000. The take a look at will fail.

const powerLevel = () => {
  const energy = 5000;

  if (energy > 9000) {
    return true;
  } else {
    return false;
  }
};

Identical variety of work days take a look at

This assessments checks that staff are working an equal quantity of days.

Two staff are at present working 4 days every, giving us a complete of eight days mixed. To see the take a look at fail, simply enter or take away some days from the arrays so they’re now not the identical size.

take a look at('staff have an equal variety of work days', () => {
  const employeeOne = ['Monday', 'Tuesday', 'Wednesday,', 'Thursday'];

  const employeeTwo = ['Friday', 'Saturday'];

  return assert.equal(workSchedule(employeeOne.size, employeeTwo.size), 8);
});

Utilizing Jest to check backend code

Now, let’s do some backend testing utilizing the Jest testing library.

Challenge setup

Open your BASH utility and cd to your most well-liked listing. Run the instructions beneath to scaffold your venture:

mkdir jest-backend-testing
cd jest-backend-testing
npm init -y
npm i categorical http-errors jest nodemon supertest
mkdir routes
contact routes/merchandise.js
contact app.js app.take a look at.js server.js

Now, open the venture in your code editor and add the code beneath into their corresponding information.

Under is code for the file routes/product.js:

const categorical = require('categorical');

const router = categorical.Router();

const createError = require('http-errors');

// Merchandise Array

const merchandise = [{ id: '1', name: 'Playstation 5', inStock: false }];

// GET / => array of things

router.get("https://weblog.logrocket.com/", (req, res) => {
  res.json(merchandise);
});

// GET / => gadgets by ID

router.get('/:id', (req, res, subsequent) => {
  const product = merchandise.discover(
    (product) => product.id === String(req.params.id)
  );

  // GET /id => 404 if merchandise not discovered

  if (!product) {
    return subsequent(createError(404, 'Not Discovered'));
  }

  res.json(product);
});

router.submit("https://weblog.logrocket.com/", (req, res, subsequent) => {
  const { physique } = req;

  if (typeof physique.title !== 'string') {
    return subsequent(createError(400, 'Validation Error'));
  }

  const newProduct = {
    id: '1',

    title: physique.title,

    inStock: false,
  };

  merchandise.push(newProduct);

  res.standing(201).json(newProduct);
});

module.exports = router;

Subsequent, the code for the file app.js:

const categorical = require('categorical');

const productsRoute = require('./routes/merchandise');

const app = categorical();

app.use(categorical.urlencoded({ prolonged: false }));

app.use(categorical.json());

app.use("https://weblog.logrocket.com/", productsRoute);

module.exports = app;

Under is the code for the file app.take a look at.js:

const request = require('supertest');

const app = require('./app');

describe('GET /', () => {
  it('GET / => array of things', () => {
    return request(app)
      .get("https://weblog.logrocket.com/")

      .count on('Content material-Sort', /json/)

      .count on(200)

      .then((response) => {
        count on(response.physique).toEqual(
          count on.arrayContaining([
            expect.objectContaining({
              id: expect.any(String),

              name: expect.any(String),

              inStock: expect.any(Boolean),
            }),
          ])
        );
      });
  });

  it('GET / => gadgets by ID', () => {
    return request(app)
      .get('/1')

      .count on('Content material-Sort', /json/)

      .count on(200)

      .then((response) => {
        count on(response.physique).toEqual(
          count on.objectContaining({
            id: count on.any(String),

            title: count on.any(String),

            inStock: count on.any(Boolean),
          })
        );
      });
  });

  it('GET /id => 404 if merchandise not discovered', () => {
    return request(app).get('/10000000000').count on(404);
  });

  it('POST / => create NEW merchandise', () => {
    return (
      request(app)
        .submit("https://weblog.logrocket.com/")

        // Merchandise ship code

        .ship({
          title: 'Xbox Collection X',
        })

        .count on('Content material-Sort', /json/)

        .count on(201)

        .then((response) => {
          count on(response.physique).toEqual(
            count on.objectContaining({
              title: 'Xbox Collection X',

              inStock: false,
            })
          );
        })
    );
  });

  it('POST / => merchandise title appropriate knowledge sort verify', () => {
    return request(app).submit("https://weblog.logrocket.com/").ship({ title: 123456789 }).count on(400);
  });
});

Virtually there! Right here’s the code for the server.js file:

const app = require('./app');

const port = course of.env.PORT || 3000;

app.pay attention(port, () =>
  console.log(`Server operating on port ${port}, http://localhost:${port}`)
);

Lastly, add these run scripts to your bundle.json file.

"scripts": {

"begin": "node server.js",

"dev": "nodemon server.js",

"take a look at": "jest --watchAll"

},

The begin script runs the server file utilizing node.

The dev script runs the server file utilizing nodemon, enabling automated reloading.

The take a look at script runs the take a look at runner Jest that routinely watches for file modifications.

Working Jest assessments

It’s time to begin the applying and take a look at runner. Run the instructions beneath in several tabs or home windows so you’ve gotten one script operating the event server and the opposite operating the Jest take a look at runner.

The server is operating on http://localhost:3000/:

npm run dev

npm run take a look at

It is best to now have the dev server operating. The Jest take a look at runner must also be operating with 5 passing assessments. Let’s undergo every of the assessments you’ll be able to see them move or fail.

The assessments have the identical title because the headings, so they need to be pretty straightforward to seek out within the information.

Array of things take a look at

This take a look at checks to see if an array of objects is returned. To see it fail, open the merchandise.js file and change the route on the prime with the code beneath:

router.get("https://weblog.logrocket.com/", (req, res) => {
  res.ship('merchandise');
});

It is best to get the error anticipated Content material-Sort" matching /json/, bought "textual content/html; charset=utf-8 and the take a look at ought to fail.

Now attempt altering it to the code beneath:

router.get("https://weblog.logrocket.com/", (req, res) => {
  res.json('merchandise');
});

It is best to get this error Anticipated: ArrayContaining [ObjectContaining {"id": Any<String>, "inStock": Any<Boolean>, "name": Any<String>}].

Gadgets by id take a look at

This take a look at checks to see if an merchandise is returned with the right id. Change the merchandise array on the prime of the file in merchandise.js to an id that may be a quantity (as an alternative of a string) to see it fail:

const merchandise = [{ id: 1, name: 'Playstation 5', inStock: false }];

It is best to get this error: anticipated "Content material-Sort" matching /json/, bought "textual content/html; charset=utf-8".

Merchandise not discovered take a look at

This take a look at checks to see if an merchandise can’t be discovered. To see it fail, change the 404 error code to one thing else within the merchandise.js file, like within the instance beneath:

if (!product) {
  return subsequent(createError(400, 'Not Discovered'));
}

It is best to get the error: anticipated 404 "Not Discovered", bought 400 "Unhealthy Request".

Appropriate knowledge take a look at

This take a look at checks if the article has appropriate knowledge and knowledge varieties. To see it fail, open the app.take a look at.js file and change the ship code with the code beneath:

.ship({

title: 'Nintendo Change',

})

It is best to see this error:

 - Anticipated  - 2
    + Obtained  + 3

    - ObjectContaining {
    + Object {
    +   "id": "1",
        "inStock": false,
    -   "title": "Xbox Collection X",
    +   "title": "Nintendo Change",

Appropriate knowledge sort take a look at

This take a look at checks to see if the title variable is the right knowledge sort. It ought to solely fail if a string is detected. To see the take a look at fail, open the app.take a look at.js file, scroll to the underside, and alter the quantity to a string like this:

return request(app).submit("https://weblog.logrocket.com/").ship({ title: '123456789' }).count on(400);

It is best to get this error: anticipated 400 "Unhealthy Request", bought 201 "Created".

Jest 28: New options

Jest 28 was launched in April 2022 and introduced alongside numerous new options. Some of the requested options is named sharding. Basically, sharding enables you to cut up your take a look at suite into totally different shards to run a fraction of your suite assessments.

For instance, to run a 3rd of your assessments, you can use the instructions beneath:

jest --shard=1/3
jest --shard=2/3
jest --shard=3/3

Conclusion

That’s all! We simply went over an introduction to testing on the backend utilizing Node and Jest. What we coated are simply the fundamentals of testing – there may be a lot extra to be taught! You’ll be able to try the official documentation for Jest right here.