To test your refrigerator water line, first turn off the water to your refrigerator. Next, disconnect the water line from the fridge. Place a cup underneath the disconnected end of the water line to catch any water that may drip out. Turn on the water to your refrigerator and check for leaks. If there are no leaks, then your refrigerator water line is working properly. If there are leaks, then you will need to replace the water line.