Merge pull request #312 from Shopify/uniq_filter

uniq filter

test/integration/standard_filter_test.rb

@@ -128,6 +128,13 @@ class StandardFiltersTest < Minitest::Test
     assert_equal [{"a" => "10"}, {"a" => "2"}], @filters.sort([{"a" => "10"}, {"a" => "2"}], "a")
   end
 
+  def test_uniq
+    assert_equal [1,3,2,4], @filters.uniq([1,1,3,2,3,1,4,3,2,1])
+    assert_equal [{"a" => 1}, {"a" => 3}, {"a" => 2}], @filters.uniq([{"a" => 1}, {"a" => 3}, {"a" => 1}, {"a" => 2}], "a")
+    testdrop = TestDrop.new
+    assert_equal [testdrop], @filters.uniq([testdrop, TestDrop.new], 'test')
+  end
+
   def test_reverse
     assert_equal [4,3,2,1], @filters.reverse([1,2,3,4])
   end