use set for sources

Author: razum2um

lib/appraisal/gemfile.rb

@@ -11,7 +11,7 @@ class Gemfile
     attr_reader :dependencies
 
     def initialize
-      @sources = []
+      @sources = Set.new
       @ruby_version = nil
       @dependencies = DependencyList.new
       @gemspec = nil

spec/appraisal/gemfile_spec.rb

@@ -14,7 +14,15 @@
     gemfile = Appraisal::Gemfile.new
     gemfile.source "one"
     gemfile.source "two"
-    expect(gemfile.to_s.strip).to eq %{source "one"\nsource "two"}
+    expect(gemfile.to_s.strip).to match %r{source "one"}
+    expect(gemfile.to_s.strip).to match %r{source "two"}
+  end
+
+  it "ignores duplicate sources" do
+    gemfile = Appraisal::Gemfile.new
+    gemfile.source "one"
+    gemfile.source "one"
+    expect(gemfile.to_s.strip).to eq %{source "one"}
   end
 
   it "preserves dependency order" do