scope = oscilloscope

The scope is a vital tool to verify that your uC is working as it should. With it you can see that clock pulses are being generated, data is going out, data is coming back (or maybe not?) AND you can verify that the timing of these signals matches the datasheet of the RTC that you are using.

Additionally, you can check the RTC's crystal to see if it is oscillating. You likely won't be able to detect much else unless it has some default programming conditions such as an output which is some programmable divide of the input clock.

Ultimately your confirmation that the RTC is working is when you can read and write to it, and see that the time is changing properly.

Dennis