@Test
public void fetch_test() {

    String url = "https://example.com/webauthn/options";
    RestTemplate restTemplate = mock(RestTemplate.class);
    when(restTemplate.getForObject(eq(url), eq(String.class))).thenReturn("response");
    RestTemplateAdaptorHttpClient httpClient = new RestTemplateAdaptorHttpClient(restTemplate);
    httpClient.fetch(url);
    verify(restTemplate).getForObject(eq(url), eq(String.class));
}