public void AddFindConverter()
        {
            converters.Add(new StringConverter(), typeof(string), typeof(int));
            var found = converters.Find(typeof(string), typeof(int));

            Assert.NotNull(found);
            Assert.IsType <StringConverter>(found);
        }
        public void FindSourceTypeNullException()
        {
            var ex = Assert.Throws <ArgumentNullException>(() =>
            {
                converters.Find(null, typeof(int));
            });

            Assert.Equal("source", ex.ParamName);
        }