### Question:
CoderUtil { public static String decodeBase64(String source) { return new String(Bytes.base642bytes(source)); }  static String MD5_16bit(String input); static String MD5_32bit(String input); static String MD5_32bit(byte[] input); static String decodeBase64(String source);  }### Answer:
@Test public void decodeBase64() { try { CoderUtil.decodeBase64(null); fail("when param is null, this should throw exception"); } catch (Exception e) { } String input = "ZHViYm8="; String output = "dubbo"; assertEquals(output, CoderUtil.decodeBase64(input)); }