public void GetValidItems_GivenTwoDictionaries_ReturnsUncommonItems()
        {
            var legacy = new LegacyClass();
            var dict1  = new Dictionary <int, int>()
            {
                { 1, 0 }, { 2, 0 }, { 3, 0 }
            };
            var dict2 = new Dictionary <int, int>()
            {
                { 7, 0 }, { 8, 0 }, { 9, 0 }, { 1, 800 }
            };
            var validItem      = legacy.GetValidItems(dict1, dict2);
            var expectedResult = new Dictionary <int, int>()
            {
                { 2, 0 }, { 3, 0 }
            };

            Assert.Equal(validItem, expectedResult);
        }