### Question:
SecureLogin { public static SecureLogin getInstance() { return instance; } private  SecureLogin(); static SecureLogin getInstance(); UserGroupInformation getLoginUser(RequestContext context, Configuration configuration); UserGroupInformation getLoginUser(String serverName, String configDirectory, Configuration configuration); boolean isUserImpersonationEnabled(Configuration configuration); static final String CONFIG_KEY_SERVICE_PRINCIPAL; static final String CONFIG_KEY_SERVICE_KEYTAB; static final String CONFIG_KEY_SERVICE_USER_IMPERSONATION; static final String CONFIG_KEY_SERVICE_USER_NAME; }### Answer:
@Test public void testSingleton() { assertSame(secureLogin, SecureLogin.getInstance()); }