Failed O2 sensor = fail e-test?

Hi guys,

I just found out I have to get an emission test done. However, I've been driving around with this CEL caused by a fault in the rear catalytic converter. The shop I go to tell me it could be because of a failed oxygen sensor or a bad cat. I'm hoping it is the sensor because I was quoted $2,300 for a new cat.

I recall someone telling me a failed O2 sensor means an automatic fail on emission testing. Is it true?

Thanks.