Adds bookmark catalogue

app/bookmarks/bookmark.rb

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+class Bookmark < Struct.new(:url)
+end

app/bookmarks/bookmark_catalogue.rb

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+class BookmarkCatalogue
+  def bookmark(attrs = {})
+    url = attrs[:url]
+
+    raise BookmarkInvalid if url.blank?
+
+    bookmarks << Bookmark.new(url)
+  end
+
+  def bookmarks
+    @@bookmarks ||= []
+  end
+
+  def clear
+    @@bookmarks = []
+  end
+end

app/bookmarks/bookmark_invalid.rb

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+class BookmarkInvalid < StandardError
+end

spec/bookmarks/bookmark_catalogue_spec.rb

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+require 'spec_helper'
+
+describe BookmarkCatalogue do
+  verify_contract(:bookmark_catalogue)
+
+  let(:bookmark_catalogue) { isolate(BookmarkCatalogue) }
+
+  before { bookmark_catalogue.clear }
+
+  it "saves bookmarks" do
+    bookmark_catalogue.bookmark(url: "cool.site")
+    bookmark_catalogue.bookmarks.should include(Bookmark.new("cool.site"))
+  end
+
+  it "is empty prior to bookmarking" do
+    bookmark_catalogue.bookmarks.should be_empty
+  end
+
+  it "raises exception with invalid url" do
+    expect {
+      bookmark_catalogue.bookmark(url: "")
+    }.to raise_error(BookmarkInvalid)
+  end
+
+  it "persists the bookmarks" do
+    isolate(BookmarkCatalogue).bookmark(url: 'cool.site')
+    isolate(BookmarkCatalogue).bookmarks.should_not be_empty
+  end
+end