How to check the FFT results of a sine wave?

I have given a audio file (sine wave)800 Hz as an input to my FFT
algorithm.I have got 8192 power spectrum samples in a array .What is the
best and easy way to check whether my output is right or wrong.If i give a
silent audio file. The out out is zero for all samples.In a sine wav the
o/p increases from 20 (0th sample )to 26059811(743 sample) and decreases
gradually to 40.Any ideas will be more helpful.If i get an idea of the
output range then i can prove technically that FFT is working or not.Any
ideas will be more helpful.

Refer
http://stackoverflow.com/questions/4040918/how-to-check-the-fft-results-in-iphone
for any technical doubts