C24 Calculator

This is a demo calculator I built with Ruby on Rails and JavaScript for a code test I was assigned during a job interview. I completed the code in 3 hours.

I was prepared to do more of a heavy back-end program. But when I received the assignment I realized that a heavy backend was overkill. So I opted to keep the framework light and ended up writing most of it in simple JavaScript.

Future considerations

Since the operators were only a few and well defined, I simply put the calculation of them in a single javascript. But if we wanted to expand the functionality of the calculator, it would make sense to create an interface for operators and have all specific operators implement the interface.

Testing

There are two sections for testing: front-end and back-end.

Front-end tests

Front-end tests are written below and manually performed.

All tests have the starting point of restarting the app.

• Test display at start of app Display should read: 0

• Test simple number entry Enter "8" "6" "5" Display should read: 865

• Test clear Enter "8" "6" "5" "c" Display should read: 0

• Test decimal Enter "8" "6" "." "5" Display should read: 86.5

• Test multiple decimals are ignored Enter "8" "." "6" "." "5" "." Display should read: 8.65

• Test negation Enter "8" "6" "5" "-" Display should read: -865

• Test reverse negation Enter "8" "6" "5" "-" "-" Display should read: 865

• Test entry to operand list Enter "5" "6" "Enter" Operand list should read: 56

• Test entering multiple operands with decimals and negatives Enter "5" "6" "Enter" "4" "1" "-" "Enter" "3" "." 1" "Enter" Operand list should read: 56 -41 3.1

• Test reseting operation Enter "5" "6" "Enter" "4" "1" "-" "Enter" "New" Operand list should be empty. Operator and Result should be empty.

• Test sum of two numbers Enter "5" "Enter" "6" "Enter" "Sum" Operands: 5 6 Operator: SUM Result: 11

• Test sum with a negative Enter "5" "Enter" "6" "-" "Enter" "Sum" Operands: 5 6 Operator: SUM Result: -1

• Test sum with a decimal Enter "5" "Enter" "6" "." "1" "Enter" "Sum" Operands: 5 6 Operator: SUM Result: 11.1

• Test mean Enter "5" "Enter" "6" "-" "Enter" "Mean" Operands: 5 6 Operator: MEAN Result: 5.5

• Test mean with no operands Enter "Mean" Operands: Operator: MEAN Result: 0

Back-end tests

Back-end tests are unit tests written in MiniTest. They can be executed by running:

rake test