This will be a ping pong exercise, which means you'll be paired up with the person sitting next to you, and only one of you can have your computer open at a time - it is probably easiest to just share the machine.

For each task, one person (p1) will take 10 minutes to write some tests before passing the laptop over to the other (p2) to write the code to pass the tests. After the tests have all been passed, the first person (p1) who will then write more tests. Repeat this process until the task is complete.

When moving onto each new task, you should swap roles. So p1 does even numbered tasks and p2 does odd numbered tasks.

##Getting Started

• P1 should Fork and clone this repository
• P2 should either share the same machine or be added as a collaborator on the forked repo, so they can clone, pull and push
• Run bundle install to install dependencies
  • Run rspec to run tests
  • Run rubocop to lint code

A skeleton application is provided as starter code.

You are required to build a Calculator class (calculator.rb) and a test suite for it (calculator_spec.rb). Specifically, an instance of the Calculator class will store a single read_only instance variable that represents the result of any methods called on it. Your tasks will be to add various mathematical functions to the class through a TDD process. As the writer of tests your intention is to create tests that force a robust implementation. As the writer of the code to pass the test, you want to implement the bare minimum to pass the test.

0. Initialize: my_calculator = Calculator.new(1) would assign 1 to the be the starting result of the new my_calculator instance.
1. Results: my_calculator.result would return the current result - it should be readonly.
2. Reset: my_calculator.reset(x) would reset the calculator to x.
3. Addition: my_calculator.add(x) would add x to the internal result value, if x can be a valid number
4. Subtraction: my_calculator.subtract(x) would subtract x from the internal result value, if x can be a valid number
5. Multiply: my_calculator.multiply(x) would multiply x by the internal result value and save the new value, if x can be a valid number
6. Divide: my_calculator.divide(x) would divide the internal result value by x and save the new value, if x can be a valid number
7. Chain: my_calculator.add(x).subtract(y) all methods should be chainable in any order
8. Operation: my_calculator.operation('add', x) would apply the addition operation with the value of x. It should support all operations
9. Undo: my_calculator.undo should undo the previous operation, restoring the result value.
10. Redo: my_calculator.redo should redo the previously undone operation, restoring the result value. If a new action is executed it should remove the ability to perform redos.

• Rspec
• Ruby Styleguide
• Programming Ruby - The Pragmatic Programmer's Guide

1. All content is licensed under a CC-BY-NC-SA 4.0 license.
2. All software code is licensed under GNU GPLv3. For commercial use or alternative licensing, please contact [email protected].