### Question:
ZTSImpl implements KeyStore, ZTSHandler { boolean isAuthorizedProxyUser(Set<String> proxyUsers, String principal) { if (proxyUsers == null) { return false; } return proxyUsers.contains(principal); } ZTSImpl();  ZTSImpl(CloudStore implCloudStore, DataStore implDataStore); @Override String getPublicKey(String domain, String service, String keyId); ServiceIdentity getServiceIdentity(ResourceContext ctx, String domainName, String serviceName); PublicKeyEntry getPublicKeyEntry(ResourceContext ctx, String domainName,
            String serviceName, String keyId); ServiceIdentityList getServiceIdentityList(ResourceContext ctx, String domainName); HostServices getHostServices(ResourceContext ctx, String host); Response getDomainSignedPolicyData(ResourceContext ctx, String domainName, String matchingTag); TenantDomains getTenantDomains(ResourceContext ctx, String providerDomainName,
            String userName, String roleName, String serviceName); @Override RoleToken getRoleToken(ResourceContext ctx, String domainName, String roleNames,
            Integer minExpiryTime, Integer maxExpiryTime, String proxyForPrincipal); @Override AccessTokenResponse postAccessTokenRequest(ResourceContext ctx, String request); RoleAccess getRoleAccess(ResourceContext ctx, String domainName, String principal); @Override RoleToken postRoleCertificateRequest(ResourceContext ctx, String domainName,
            String roleName, RoleCertificateRequest req); @Override RoleCertificate postRoleCertificateRequestExt(ResourceContext ctx, RoleCertificateRequest req); AWSTemporaryCredentials getAWSTemporaryCredentials(ResourceContext ctx, String domainName,
            String roleName, Integer durationSeconds, String externalId); @Override Response postInstanceRegisterInformation(ResourceContext ctx, InstanceRegisterInformation info); @Override InstanceIdentity postInstanceRefreshInformation(ResourceContext ctx, String provider,
            String domain, String service, String instanceId, InstanceRefreshInformation info); @Override void deleteInstanceIdentity(ResourceContext ctx, String provider,
            String domain, String service, String instanceId); @Deprecated @Override Identity postInstanceRefreshRequest(ResourceContext ctx, String domain,
            String service, InstanceRefreshRequest req); @Override Response postSSHCertRequest(ResourceContext ctx, SSHCertRequest certRequest); @Override JWKList getJWKList(ResourceContext ctx, Boolean rfc); @Deprecated @Override Identity postOSTKInstanceRefreshRequest(ResourceContext ctx, String domain,
            String service, OSTKInstanceRefreshRequest req); @Override ResourceAccess getResourceAccessExt(ResourceContext ctx, String action, String resource,
            String trustDomain, String checkPrincipal); @Override ResourceAccess getResourceAccess(ResourceContext ctx, String action, String resource,
            String trustDomain, String checkPrincipal); @Override Access getAccess(ResourceContext ctx, String domainName, String roleName,
            String principal); CertificateAuthorityBundle getCertificateAuthorityBundle(ResourceContext ctx, String name); @Override DomainMetrics postDomainMetrics(ResourceContext ctx, String domainName,
            DomainMetrics domainMetrics); @Override Status getStatus(ResourceContext ctx); @Override Schema getRdlSchema(ResourceContext context); ResourceContext newResourceContext(HttpServletRequest request,
                                              HttpServletResponse response,
                                              String apiName); static String getRootDir(); void recordMetrics(ResourceContext ctx, int httpStatus);  }### Answer:
@Test public void testIsAuthorizedProxyUser() { assertFalse(zts.isAuthorizedProxyUser(null, "user.joe")); Set<String> proxyUsers = new HashSet<>(); proxyUsers.add("user.joe"); proxyUsers.add("user.jane"); assertTrue(zts.isAuthorizedProxyUser(proxyUsers, "user.joe")); assertTrue(zts.isAuthorizedProxyUser(proxyUsers, "user.jane")); assertFalse(zts.isAuthorizedProxyUser(proxyUsers, "user.john")); }