• There are two players in the game (X and O)
• Players take turns until the game is over
• A player can claim a field if it is not already taken
• A turn ends when a player claims a field
• A player wins if they claim all the fields in a row, column or diagonal
• A game is over if a player wins
• A game is over when all fields are taken

Build the business logic for a game of tic tac toe. It should be easy to implement a working game of tic tac toe by combining your code with any user interface, whether web or command line.

1. Install gems using 'bundle install'
2. Use 'rspec' to run tests with SimpleCov checking the coverage - coverage should be higher than 95%
3. If all tests pass, run 'rubocop' to check the readability of code

• Code is structured in three classes
• Game class controls the players turns and where they place their pieces on the board
• Calculation class checks the array to see if the latest move resulted in a win
• Results class send the result of a winning turn back to Game to announce the winner