Need Help with FFT code

In any dsp module testing is same, you get stimulus input then its reference output from a software tool e.g. Matlab then pass same input to your module and check outputs for errors. You need a testbench to read stimulus file and ref file then compare.

For fft use Matlab fft, just one statement:

y = fft(x,64);

however you need care to get frame boundaries (64 data frame) correct between Matlab and module. You also need match scaling issue and fft centre(dc centred or not)