the method of verification of IP on FPGA

I want to implement the IP of I2C on Altera's FPGA. I have some questiones about verification of the IP. what it is correctly method that can verifying the IP roundly?

I have just only think it be tested through connecting to external IC, If they can be communicated, the IP can be used, but It's not be called on verification of IP, I think. Please give me a little hint.Thanks!