@Test
public void testNullSaltOrInfo() throws Exception {

  byte[] ikm = Random.randBytes(20);
  byte[] info = Random.randBytes(20);
  int size = 40;
  byte[] hkdfWithNullSalt = Hkdf.computeHkdf("HmacSha256", ikm, null, info, size);
  byte[] hkdfWithEmptySalt =  Hkdf.computeHkdf("HmacSha256", ikm, new byte[0], info, size);
  assertArrayEquals(hkdfWithNullSalt, hkdfWithEmptySalt);
  byte[] salt = Random.randBytes(20);
  byte[] hkdfWithNullInfo = Hkdf.computeHkdf("HmacSha256", ikm, salt, null, size);
  byte[] hkdfWithEmptyInfo =  Hkdf.computeHkdf("HmacSha256", ikm, salt, new byte[0], size);
  assertArrayEquals(hkdfWithNullInfo, hkdfWithEmptyInfo);
}