as you may know i want to check it's full ability.
How would we know that?
Have you seen the Atmega328P datasheet?
660 pages long describing all the capabilities it has. Would take a while and require several different pieces of test hardware to check it all out: SPI interface, I2C interface, analog inputs, PWM outputs, digital IO, interrupts, and so on.
Write yourself a couple of test sketches:
Make sure you can interact with the serial monitor at different speeds.
Make sure you can blink an LED on each pin, will give you some confidence all the output drivers are working.
Make sure you can read a high & low on each pin, will will give you some confidence all the input pins are working.
Make sure you can read all the analog pins as you vary a pot from 0 to 5V, will will give you some confidence all the analog pins and analog mux and ADC are working.
Make sure you can both INTs and PCINTs on all pins.
Make sure you can interface with an I2C device.
Make sure you can interface with an SPI device.
etc.
That should keep you busy for a while to start.