add tests for these methods: to_s,to_json, and self.from_json

spec/book_spec.rb

@@ -1,5 +1,6 @@
 require_relative '../lib/classes/book'
 require 'rspec'
+require 'json'
 describe Book do
   before(:each) do
     @book8 = Book.new('2013-02-12', 'Orbit', 'Good', archived: false)

spec/genre_spec.rb

@@ -17,4 +17,33 @@
       expect(new_genre.items.length).to eq 1
     end
   end
+
+  describe "#to_json" do
+    it "converts to json" do
+      cart = Genre.new("My Cart")
+      cart.items << Item.new("Item 1")
+
+      expect(cart.to_json).to eq({
+        name: "My Cart",
+        items: [cart.items[0].to_json] 
+      }.to_json)
+    end
+  end
+
+  describe "#to_s" do
+    it "returns string with id and name" do
+      cart = Genre.new("My Cart")
+
+      expect(cart.to_s).to eq("Id: #{cart.id}, Name: My Cart")
+    end
+  end
+
+  describe ".from_json" do
+    it "creates a Cart from json" do
+      json = {name: "My Cart"}.to_json
+      cart = Genre.from_json(JSON.parse(json))
+
+      expect(cart.name).to eq("My Cart")
+    end
+  end
 end