I'm involved with an effort to implement an FFT algorithm, and am curious what the recommended advice is for the input test data to use -- and why! -- and what accuracy to expect.
On test inputs, I've found a little guidance in old Usenet posts that I'll post as an answer, but it's just one person's suggestions without a lot of justification -- I haven't found anything that looks like a solid answer.
On accuracy, Wikipedia says that the error should be O(e log N), but what's a reasonable expectation in absolute terms?
Edit to add: The actual tests are in a form where I have stored arrays of input data and pre-computed "reference" output data to compare to, so I don't necessarily need something with a closed-form solution.