Statistical Analysis of Cryptographic Hashing Algorithms I was wondering how can I use NIST Statistical Test Suite to check for the randomness of output generated by a cryptographic hashing algorithm, let say SHA-256?

To be specific, how will I generate input for the suite? For block ciphers, we use key avalanche, plaintext and ciphertext avalanche, etc as inputs of the suite. Is same kind of inputs are used while evaluating a cryptographic hash algorithm, as for an S-box or block cipher?
You simply create a hashed counter.  So output = SHA-256(n) whilst incrementing n. You'd make n a large multi-byte variable, say 16 bytes, and seed it at a random value from some PRNG you find lying around. That way you can perform repeat runs to generate different sequences. I find that you need >10MB for some of the template tests to complete fully.

I won't bother repeating  Natanael's comment to you :-)