Your supermarket sells drinks, crisps and sandwiches. It also offers a meal deal, where one of each items can be purchased for £3.00. You need to be able to calculate the price of a basket of items, based on the prices on the item classes, and the special meal deal rule.
Implement the class BasketPriceCalculator to return the correct values. The PHPSpec tests provided should pass when
you have done this correctly.
The tests can be run with ./tests.sh. If that gets annoying, ./vendor/bin/phpspec run will achieve much the same
thing, without audio prompts.