public void And()
{
Result <int, Exception> res1 = new Ok <int, Exception>(1);
Assert.Equal(2, res1.And(new Ok <int, Exception>(2)).Unwrap());
Assert.Equal(typeof(Err <string, Exception>), res1.And(new Err <string, Exception>(new Exception("this is test."))).GetType());
Result <int, Exception> res2 = new Err <int, Exception>(new Exception("this is test."));
Assert.Equal(typeof(Err <string, Exception>), res2.And(new Ok <string, Exception>("string value.")).GetType());
Assert.Equal(typeof(Err <string, Exception>), res2.And(new Err <string, Exception>(new Exception("this is test."))).GetType());
}