Unit Testing - JavaScript

Unit testing a simple JavaScript function.

Objective:

The objective of the project was to write unit tests for the below JavaScript function:

var fizzBuzz = function( test ){
  if ( test % 3 === 0 ){
    return 'Fizz';
  } else if (test % 5 === 0 ){
    return 'Buzz';
  }
  return '';
}

Tech Stack:

The application uses the following technologies:

• JavaScript
• bash
• Jest - testing framework for JavaScript

Installation & Dependencies:

1. Clone the github.com/erincameron11/health-information github repo in your terminal
2. Navigate to the folder unit-test
3. Install npm using the command: npm install
   • If you do not have npm installed, first download nodejs: https://nodejs.org/en/download/. To check if you have it installed type command node -v
4. Install jest to perform the unit tests locally: npm install --save-dev jest in your terminal

Run:

1. To run the test locally, perform the command: npm test in your terminal

Output:

Once the tests have been run in the terminal, the output will look something like below:

Problem Breakdown

To simplify the problem, I first deconstructed the function into pseudocode/plain english to understand the logic:
if test is a multiple of 3, return Fizz
if test is not a multiple of 3, but is a multiple of 5, return Buzz
if test is not a multiple of 3 or 5, return empty string

Unit Tests

I then wrote the following unit tests to test the fizzBuzz function:

Testing an input of 3, expected result ‘Fizz’:

test('test = 3; output should be Fizz', () => {
  const result = fizzBuzz(3);
  expect(result).toBe("Fizz");
});

Testing an input of 5, expected result ‘Buzz’:

test('test = 5; output should be Buzz', () => {
  const result = fizzBuzz(5);
  expect(result).toBe("Buzz");
});

Testing an input of string, expected result empty string:

test('test = "Hello"; output should be empty string', () => {
  const result = fizzBuzz("Hello");
  expect(result).toBe("");
});

Testing an input of a different data structure (array), expected result empty string:

test('test = [1, 2, 3, 4]; output should be empty string', () => {
  `const result = fizzBuzz([1, 2, 3, 4]);
  `expect(result).toBe("");
`});

Testing an input of a different data structure (array with different index values), expected result empty string:

test('test = [3, 30, 15, 9]; output should be empty string', () => {
  const result = fizzBuzz([3, 30, 15, 9]);
 expect(result).toBe("");
});

Testing an input of 30 (multiple of both 3 and 5), expected result ‘Fizz’:

test('test = 30; output should be Fizz', () => {
  const result = fizzBuzz(30);
  expect(result).toBe("Fizz");
});

Testing an input of 1.2, expected result empty string:

test('test = 1.2; output should be empty string', () => {
  const result = fizzBuzz(1.2);
  expect(result).toBe("");
});

Testing an input of 0, expected result ‘Fizz’:

test('test = 0; output should be Fizz', () => {
  const result = fizzBuzz(0);
  expect(result).toBe("Fizz");
});

Conclusion

The function passes all 8 proposed unit tests.

The original fizzBuzz function could be enhanced by accounting for results that are true for both “Fizz” and “Buzz”. For example:

var fizzBuzz = function( test ){
  if ( test % 3 === 0 &&  test % 5 === 0 ){
    return 'FizzBuzz';
  } else if ( test % 3 === 0 ){
    return 'Fizz';
  } else if (test % 5 === 0 ){
    return 'Buzz';
  }
    return '';
}