public void FilterString_ToUpper_Converts_Value_To_UpperCase()
{
var filter = new FilterString();
filter.Value = null;
filter.ToUpper();
Assert.IsNull(filter.Value);
filter.Value = "";
filter.ToUpper();
Assert.AreEqual("", filter.Value);
filter.Value = "Abc";
filter.ToUpper();
Assert.AreEqual("ABC", filter.Value);
}