Adding a failing test for Pizza::Topping.initialize.
Add a failing test for Pizza::Topping.new 'bell peppers', vegetarian: true (a keyword argument)
Add code that passes test for Pizza::Topping.new 'bell peppers', vegetarian: true.
Add failing test for Pizza::Pie.initialize method that creates an array with toppings.
Add initialize method to Pizza::Pie to pass test.
Add failing test for Pizza::Pie.new for default to cheese when no toppings given.
Add default value of cheese and vegetarian to Pizza::Pie.new if no toppings are given.