Added test for '2' button
Added simple solution for '2' key
Refactored implementation of digit keys to remove duplication
Added general test case for digit keys
Added the missing digit key functions
Removed the (now) redundant digit button tests
Added the first test for the equals operator
Added simplest solution for the equals button
Simplified the existing equals test
Added test for digit key presses after equals
Added call to equals() to the last test
Made the next digit key press start a new number after equals is pressed
Added tests for the plus button which equivalent to the equals button
Just made plus and equals the same function to make the tests pass
Added test for simple addition of 2 integer numbers
Implemented plus() function
Added test for adding sequences of numbers
Changed test prior to renaming cancel() to cancelEntry()
Renamed cancel() to cancelEntry()
Added test for AC-All Clear function