A memory testing circuit and method are disclosed, the redesigning of a memory to be tested through incorporation therein a testing circuit includes a self-test circuit incorporating a decoder circuit, and a VPPIO I/O module incorporating an encoder circuit and having multiple functions including digital I/O, high analog voltage I/O and current I/O. An oscillator module embedded in the multiplexer circuit provides a clock signal for the testing. The VPPIO I/O module is configured to convert, by the self-test circuit, a stimulating input from a single signal pin to a parallel signal recognizable by the memory and an analog voltage/current signal, thereby accomplishing proper testing of the memory. This enables a single signal pin to test all functions of one memory, thereby increasing the number of memory dies on a wafer tested in parallel by a test instrument and reducing the testing time per wafer as well as testing cost.