adding a test

test/pbbuilder_test.rb

@@ -30,6 +30,22 @@ class PbbuilderTest < ActiveSupport::TestCase
     assert_equal "Eggs", person.favourite_foods["Breakfast"]
   end
 
+  test "duplicated enum fields don't happen" do
+    person = Pbbuilder.new(API::Person.new) do |pb|
+      pb.field_mask do
+        pb.paths ["ok", "that's"]
+      end
+    end.target!
+
+    p = Pbbuilder.new(person) do |pb|
+      pb.field_mask do
+        pb.paths ["ok", "that's"]
+      end
+    end.target!
+
+    assert_equal(["ok", "that's"], p.field_mask.paths)
+  end
+
   test "it can extract fields in a nice way" do
     klass = Struct.new(:name)
     friends = [klass.new("Friend 1"), klass.new("Friend 2")]