Logic for adding items and validating them

.tool-versions

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+ruby 4.0.6

README.md

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 # Ruby Technical Test
 
+## Dependencies
+
+* Ruby 4.0.6
+* Minitest 6.0.6
+
+## Instructions
+
+Checkout class is in `checkout.rb`
+
+Run tests with `ruby -Ilib:test tests.rb`
+
+`main.rb` is a scratchpad
+
 ## Initial Thoughts
 
 * Cart can be stored in an array of strings

checkout.rb

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+class Checkout
+  class InvalidItem < StandardError; end
+
+  AVAILABLE_ITEMS = {
+    PI5: 60.00,
+    ZERO2W: 15.00,
+    PICO2: 4.00
+  }
+
+  def initialize
+    @items = []
+  end
+
+  def add(item)
+    raise InvalidItem unless valid_item(item)
+    @items.push item
+  end
+
+  def items
+    @items
+  end
+
+  private
+
+  def valid_item(item)
+    return AVAILABLE_ITEMS.keys.include?(item)
+  end
+end

main.rb

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+require "./checkout.rb"
+
+checkout = Checkout.new()
+
+checkout.add(:PI5)
+checkout.add(:ZERO2W)
+
+checkout.items # ["PI5", "ZERO2W"]
+checkout.total # 75.00

tests.rb

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+require "minitest/autorun"
+
+require "./checkout.rb"
+
+class TestCheckout < Minitest::Test
+  def setup
+    @checkout = Checkout.new
+  end
+
+  def test_that_unknown_items_cannot_be_added
+    assert_raises Checkout::InvalidItem do
+      @checkout.add(:foo)
+    end
+  end
+
+  def test_that_allowed_items_are_added
+    @checkout.add(:PI5)
+    @checkout.add(:ZERO2W)
+
+    assert_equal [:PI5, :ZERO2W].sort, @checkout.items.sort
+  end
+end