### Question:
RegisterAuthenticator implements RequiredActionProvider { @Override public void requiredActionChallenge(RequiredActionContext context) { String userid = context.getUser().getId(); String username = context.getUser().getUsername(); Challenge challenge = new DefaultChallenge(); String challengeValue = Base64Url.encode(challenge.getValue()); String origin = context.getUriInfo().getBaseUri().getHost(); context.getAuthenticationSession().setAuthNote(WebAuthnConstants.AUTH_CHALLENGE_NOTE, challengeValue); Response form = context.form() .setAttribute(WebAuthnConstants.ORIGIN, origin) .setAttribute(WebAuthnConstants.CHALLENGE, challengeValue) .setAttribute(WebAuthnConstants.USER_ID, userid) .setAttribute(WebAuthnConstants.USER_NAME, username) .createForm("webauthn-register.ftl"); context.challenge(form); } RegisterAuthenticator(KeycloakSession session); @Override void close(); @Override void evaluateTriggers(RequiredActionContext context); @Override void requiredActionChallenge(RequiredActionContext context); @Override void processAction(RequiredActionContext context);  }### Answer:
@Test public void test_requiredActionChallenge() throws Exception { try { authenticator.requiredActionChallenge(context); } catch (Exception e) { Assert.fail(e.getMessage()); } verify(context).challenge(any(Response.class)); }