Abstract: A device used to test the analyte in a liquid sample includes a test chamber used to contain test components, a collecting chamber used to collect liquid sample, a piston chamber between the test chamber and the collecting chamber, a piston and an opening. The piston has two positions in the piston chamber, i.e. the first position and the second position. When the piston is in the first position, liquid can flow between the piston cavity and the collecting chamber through the opening; during the piston's move from the first position to the second position, the opening is sealed by the piston, wherein while the opening is sealed by the piston, the liquid is released from the piston cavity to the test chamber. This device can help to precisely quantify a liquid sample, with higher accuracy in the tests and higher comfort during the operations.