### Question:
Jwt { public static ByteBuf header(ByteBuf token) { int length = ByteBufUtil.indexOf(token, token.readerIndex(), token.readableBytes(), JWT_SEPARATOR); return token.slice(token.readerIndex(), length); }  static ByteBuf header(ByteBuf token); static ByteBuf payload(ByteBuf token); static ByteBuf signature(ByteBuf token); static ByteBuf headerAndPayload(ByteBuf token); static boolean verifySHA256withRSA(PublicKey publicKey, ByteBuf token); static boolean verify(String alg, PublicKey publicKey, ByteBuf token); static long parseAccessKey(ByteBuf token, Set<String> mappedFields); static String parseAlgorithm(ByteBuf token);  }### Answer:
@Test public void testHeader() { ByteBuf header = Jwt.header(JWT); String s = header.toString(StandardCharsets.UTF_8); Assert.assertEquals("eyJ0eXAiOiJKV1QiLCJhbGciOiJSUzI1NiJ9", s); }