Workshop: Building a Coolculator 🔢

Collaborators: [your github username] & [your partners github username]

Make sure you’re working in pairs - on a single laptop. You’ll be pair programming. Remember, in pair programming, there are two roles - driver and navigator.

Start by forking this repo...

Forking creates a copy of this repo in your own GitHub account. Add your partner as a collaborator by going to 'Settings' > 'Collaborators & teams' and entering their GitHub username in the 'Collaborators' box. That means you'll both have access to the repo.

Next, clone down the repo onto the laptop you're working on, change into the directory and run

npm install

This will install the required dependancies, including Mocha and Chai.

To check everything is working, run the tests with

npm test

You should see something like this:

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For each of the bold questions below...

🗣 Discuss       👩‍💻 Change       👀 Observe       🔄 Repeat

Once you understand what's going on, ANSWER THE QUESTION IN THIS README FILE and make the required changes to the code.

ℹ️ Make sure you commit regularly!

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Part 1: Testing Array

Look in array.test.js. This contains some tests for JavaScript's built-in Array methods.

What do the existing tests actually test (explain in english)?

Add a test for the pop() method. Hint: You'll need two assertions to fully test that it pop() works. Explain why you chose these assersions here.

💡 REMINDER: Do you need to commit your answers to the questions above?

Part 2: The Coolculator

Until now, we've been testing JavaScript's in-built functionality, which is kinda pointless - the folks who wrote JavaScript probably already have tests for this stuff. Let's take a look at our own project: the Coolculator. This is a class that has a bunch of methods for doing calculator-like stuff.

Read The coolculator class and tests.

What methods does the Cooclulator currently implement?

Describe how the existing test works

Change a value in the add() test so it fails. Once you've seen it fail, revert your change so it's green again.

Changethe implementation of add() so it always returns 1000. Once you've seen it fail, revert your change so it's green again.

Now let's do some TDD! Uncomment the multiply() test.

What do you expect to happen when you run your tests?

What actually happened when you ran your tests?

Add a method to the Coolculator so the test passes green

Uncomment the subtract() test and write some code to make it green Remember the process: Red / Green / Refactor - is there any refactoring you could do to clean up your code?

💡 REMINDER: Do you need to commit your answers to the questions above?

Part 3: Extending the Coolculator

Add some more methods to the Coolculator class using the Red/Green/Refactor process. Be sure to write your tests first. Here are some things you could add to your calculator:

Function
divide	Takes two numbers and divides the first by the second
highest	Takes two integers and returns the highest one
lowest	Takes two integers and returns the lowest one
double	Takes a number and doubles it
square	Takes one number and squares it
raise	Takes two numbers and raises the first one to the power of the second
isNegative	Takes a number and returns true if it's negative and false if it's positive
isPositive	Takes a number and returns true if it's positive and false if it's negative
isCool	Takes a number and returns true if the number is cool (ie. starts and ends with the same digit). Should return a boolean
sum	Takes an array of numbers and adds them all
multiplyArray	Takes an array of numbers and multiplies them all
mean	Takes an array of numbers and returns the mean (average)
factorial	Takes a single number and calculates its factorial (this is kinda hard)
random	Takes an integer and returns a random integer between 0 and it. How might we test this? (This requires some thinking!, and we'll never have a perfect test)

💡 REMINDER: Do you need to commit your new code?

Part 4 (extension): More Array Tests

⚠️ Don't attempt this unless you've finished all your other work

Add some more tests for JavaScript's built-in array methods:

• indexOf()
• join()
• shift()
• unshift()
• Any others you can think of!

Part 5 (super-extension)

⚠️ Don't attempt this unless you've finished all your other work

Use TDD to adapt your add method so it takes an arbitrary number of integers as arguments, and adds them all together, eg:

add(1, 2) //=> 3
add(1, 2, 7, 10) //=> 20
add(5) //=> 5