Add basic JSON compare test

test/tests/test_json_compare.rb

+class JSONCompareTests < Test::Unit::TestCase
+  include BrakemanTester::DiffHelper
+
+  def setup
+    @path = File.expand_path "#{TEST_PATH}/apps/rails3.2"
+    @json_path = File.join @path, "report.json"
+    File.delete @json_path if File.exist? @json_path
+    Brakeman.run :app_path => @path, :output_files => [@json_path]
+    @report = JSON.parse File.read(@json_path)
+  end
+
+  def update_json
+    File.open @json_path, "w" do |f|
+      f.puts @report.to_json
+    end
+  end
+
+  def diff
+    @diff = Brakeman.compare :app_path => @path, :previous_results_json => @json_path
+  end
+
+  def test_sanity
+    diff
+
+    assert_fixed 0
+    assert_new 0
+  end
+end