public void LookupMemberTest()
{
var v1 = (NSString)"1";
var v2 = (NSString)"2";
using (var st = new NSMutableSet <NSString> (v1)) {
Assert.Throws <ArgumentNullException> (() => st.LookupMember((NSString)null), "LookupMember ANE 1");
Assert.AreSame(v1, st.LookupMember(v1), "LookupMember 1");
Assert.IsNull(st.LookupMember(v2), "LookupMember 2");
}
}