Well many of us might be having Samsung touchscreen phones.
Samsung therefore offers us a chance to maintain these
by using the LCD test.
This LCD test helps us know if there is any problem
in our phone.
NOTE:- This might not work on all Samsung Touch-screens Phones.

To check the LCD test in Samsung touch screen
1) First open the dialer
2) Dial this code - *#0*#
3) As soon as you press the second '#' the LCD test will appear.

Here is a video on using the LCD test (on Samsung Galaxy Y)