@Test
void testGetSignatureNoParameter() {

    URL url = mock(URL.class);
    Invocation invocation = mock(Invocation.class);
    String secretKey = "123456";
    AccessKeyAuthenticator helper = new AccessKeyAuthenticator();
    String signature = helper.getSignature(url, invocation, secretKey, String.valueOf(System.currentTimeMillis()));
    assertNotNull(signature);
}