Unit Testing

• A way of testing individual pieces of code called units
  • Acceptance Testing
  • system Testing
  • Integration Testing
  • Unit Testing

Jest

Let's get into some algorithms, but we will do more than just solve them. We will write unit tests using Jest to check our work

Note:

Try to understand the problem then write the test, would be much easier.

• Split the Big Problem into smaller problems
• documents them
• Gather small problems to create again the Big Problem

Starting with Jest

• install jest through npm as devDep: $ npm i -D jest
• add our script to package.json

How to create a simple test?

• Create your file 'sum.js'

  • Open the file and create a function sum that add two numbers

• Create the jest file 'sum.test.js'

• Open the sum.test.js and Require the 'sum function'

  • Now write the test function

• Now run the test: $ npm run test

Full Code:

sum.js
function sum (a, b) {
    return a + b;
}

// Export in order to require somewhere else
module.exports = sum;

sum.test.js
const sum = require('./sum');

test('Adds 1 + 2 to equal 3', () => { 
    expect(sum(1, 2)).toEqual(3);
});

Output:

$ npm run test

> data_structures_unit-test@1.0.0 test
> jest

 PASS  ./sum.test.js
  √ Adds 1 + 2 to equal 3 (8 ms)

Test Suites: 1 passed, 1 total                                                                                                                          
Tests:       1 passed, 1 total                                                                                                                          
Snapshots:   0 total
Time:        5.744 s
Ran all test suites.

Grouping Tests Together

• First put sum.js and sum.test.js in a folder 'sum'
• Second , create two files, fizzbuzz.js and fizzbuzz.test.js and put it to a new folder 'fizzbuzz'
  • Now create the fizzbuzz function within fizzbuzz.js
  • Next create the fizzbuzz test within fizzbuzz.test.js

Now its time for the final stage:

• Open terminal and run our command: $ npm run test Jest will run both functions

Code:

fizzbuzz.js

function fizzbuzz(number) {
    if (number % 3 === 0) {
        return 'Fizz';
    } else if (number % 5 === 0) {
        return 'Buzz';
    } else {
        return number;
    }
}

// Export this function

module.exports = fizzbuzz;


fizzbuzz.test.js

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

describe('fizzbuzz', ()=>{
    it('should be a function', ()=>{
        expect(typeof fizzbuzz).toEqual('function');
    });
});

Output:

$ npm run test

> data_structures_unit-test@1.0.0 test
> jest

 PASS  sum/sum.test.js
 PASS  fizzbuzz/fizzbuzz.test.js

Test Suites: 2 passed, 2 total
Tests:       2 passed, 2 total
Snapshots:   0 total
Time:        0.959 s
Ran all test suites.

Lets simulate an intention error:

• Open fizzbuzz.test.js file and change .toEqual('string);

Code

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

describe('fizzbuzz', ()=>{
    it('should be a function', ()=>{
        expect(typeof fizzbuzz).toEqual('string');
    });
});

Output:

$ npm run test

> data_structures_unit-test@1.0.0 test
> jest

 FAIL  fizzbuzz/fizzbuzz.test.js
  ● fizzbuzz › should be a function
                                                                                                                                                        
    expect(received).toEqual(expected) // deep equality

    Expected: "string"
    Received: "function"

      3 | describe('fizzbuzz', ()=>{
      4 |     it('should be a function', ()=>{
    > 5 |         expect(typeof fizzbuzz).toEqual('string');
        |                                 ^
      6 |     });
      7 | });
      8 |

      at Object.toEqual (fizzbuzz/fizzbuzz.test.js:5:33)

 PASS  sum/sum.test.js
                                                                                                                                                        
Test Suites: 1 failed, 1 passed, 2 total                                                                                                                
Tests:       1 failed, 1 passed, 2 total
Snapshots:   0 total
Time:        0.6 s, estimated 1 s
Ran all test suites.

Reverse String Algorithm

• Create a folder 'reverseString'
  • Inside of folder lets create two files, reversestring.js and reversestring.test.js Now lets add code for each file

reversestring.js
Solution 1 :
Steps:

- Create a function
- Capture ther string first as param,
- Convert that string into array,
    - .split('') without space
- Use reverse() method on an array,
- Turn it back to a string with .join('') without space

Code:

function reverseString (str) {
    return str.split('').reverse('').join('')
}

module.exports = reverseString;

Solution 2:

Code:
function(str) {
    let reversed = '';

    for (let char of str) {
        reversed = char + reversed
    }

    return reversed;
}

Solution 3:
Code:

function reverseString (str) {
    return str.split('').reduce((reversed, char)=> char + reversed, '') 
}

module.exports = reverseString

reversestring.test.js

// Require reversestring.js first
const reverseString = ('./reversestring');

// Desbribe 
describe('Reverse String', ()=> {
    // Must be a function
    it('should be a function', ()=>{
    // Expect the typeof reverseString is equal to function
    expect(typeof reverseString).toEqual('function')
    });

    // Make sure that returns a string
    it('should return a string', ()=>{
        // Invoke the reverseString() function first
        // Expect the typeof reverseString is equal to string
        expect(typeof reverseString('hello')).toEqual('string')
        });

    it('should return reversed string', ()=>{
        // Expect the typeof reverseString is equal to function
        expect(reverseString('hello')).toEqual('olleh');
        expect(reverseString('bye')).toEqual('eyb');
        expect(reverseString('endri')).toEqual('irdne');
        });
})

Palindrome Algorithm

• Check the palindrome 'folder'
• Code is explained with comments

Arraychunk Algorithm

• Check the Arraychunk 'folder'
• Code is explained with comments

Anagram Algorithm

• Check the anagram 'folder'
• Code is explained with comments

Get Element By Tag - jsdom

• Check the getElementByTag_jsdom 'folder'
• Code is explained with comments

hasDuplicateIDS - jsdom

• Check the hasDuplicatedIDs_jsdom 'folder'
• Code is explained with comments