SHA256 test suite:
SHA256 ("") = e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855
SHA256 ("a") = ca978112ca1bbdcafac231b39a23dc4da786eff8147c4e72b9807785afee48bb
SHA256 ("abc") = ba7816bf8f01cfea414140de5dae2223b00361a396177a9cb410ff61f20015ad
SHA256 ("message digest") = f7846f55cf23e14eebeab5b4e1550cad5b509e3348fbc4efa3a1413d393cb650
SHA256 ("abcdefghijklmnopqrstuvwxyz") = 71c480df93d6ae2f1efad1447c66c9525e316218cf51fc8d9ed832f2daf18b73
SHA256 ("abcdbcdecdefdefgefghfghighijhijkijkljklmklmnlmnomnopnopq") = 248d6a61d20638b8e5c026930c3e6039a33ce45964ff2167f6ecedd419db06c1
SHA256 ("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789") = db4bfcbd4da0cd85a60c3c37d3fbd8805c77f15fc6b1fdfe614ee0a7c8fdb4c0
SHA256 ("12345678901234567890123456789012345678901234567890123456789012345678901234567890") = f371bc4a311f2b009eef952dd83ca80e2b60026c8e935592d0f9c308453c813e
SHA256 (one million 'a' characters) = cdc76e5c9914fb9281a1c7e284d73e67f1809a48a497200e046d39ccc7112cd0