Client Testing

index.js

// inside __tests__ folder

const utilities = require('../index');

describe('default', () => {
  it('run the tests', () => {});
});

describe('add function', () => {
  it('should add two numbers', () => {
    // arrange
    const add = utilities.add;

    // act
    const seven = add(3, 4);
    const four = add(0, 4);
    const minusThree = add(1, -4);

    // assert
    expect(seven).toBe(7);
    expect(four).toBe(4);
    expect(minusThree).toEqual(-3);
  });

  it('checks identity', () => {
    const numbers = [1, 2, 3];

    // const actual = [1, 2, 3];
    const actual = numbers;

    expect(numbers).toBe(actual);
  });

  it('checks that it is an array', () => {
    const numbers = [1, 2, 3];
    const expected = 'array';

    const actual = Array.isArray(numbers);

    expect(actual).toBe(true);
  });
});

notes.md

(Automated) Testing

• why?
• how?
• what? comes from experience and the system we're testing and even the tech stack.
• when? test-first vs test after.

Confidence (in the sense of trusting your code). Verifying correctess.

We write code to test our code.

Why learn it?

• good for resume.
• can work on QA and DevOps.
• helps understand how an application works.
• prevents regressions.
• safety net.

Tooling: Test runner (Mocha) + assertion library (Chai).

We are using Jest.

What could happen if I have no tests.

• test manually, as the app grows, the time needed will not scale.
• regressions, code that used to work breaks.
• you just don't know if the code is correct for all cases.
• adding new features becomes slow.

Types

• unit tests. Fastest.
• integration tests.
• end to end. Slow.
• component testing. (for component based frameworks, like React, Angular, Vue, etc.)
• snapshot testing. (unique to our stack/tools)
• coverage test.
• functional testing.
• performance testing.
• aceptance test.

We'll concentrate on:

• unit
• component
• snapshot

when, then

package.json

{
  "name": "testing",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "test": "jest --watch"
  },
  "keywords": [],
  "author": "",
  "license": "ISC",
  "dependencies": {
    "jest": "^22.4.4"
  }
}

rootindex.js

// at root folder, rename to index.js had to name it this becuase two files can't have the same name on a gist

function add(a, b) {
  return a + b;
}

module.exports = {
  add: add,
};