An electronic device tester is connected to an electronic device needed to be tested. A test program is stored in a data storage of the tester. The test program includes a number of test instructions. The tester encapsulates the test instructions of the test program to a number of script files, stores the script files to the data storage, and records a name of each script file to the test program. After the test instruction is encapsulated, the tester selects desired script files of the test program and calls the selected script files according to the names of the script files to implement the test program to test the electronic device.