### Question:
HashUtils { public static boolean isValidBcryptHash(String hash) { return hash.length() > 3 && hash.substring(0, 2).equals("$2"); } private  HashUtils(); static String sha1(String message); static String sha256(String message); static String sha512(String message); static String md5(String message); static MessageDigest getDigest(MessageDigestAlgorithm algorithm); static boolean isValidBcryptHash(String hash); static String hash(String message, MessageDigest algorithm);  }### Answer:
@Test public void shouldCheckForValidBcryptHashStart() { assertThat(HashUtils.isValidBcryptHash(""), equalTo(false)); assertThat(HashUtils.isValidBcryptHash("$2afsdaf"), equalTo(true)); assertThat(HashUtils.isValidBcryptHash("$2"), equalTo(false)); assertThat(HashUtils.isValidBcryptHash("$2aead234adef"), equalTo(true)); assertThat(HashUtils.isValidBcryptHash("#2ae5fc78"), equalTo(false)); }