public void FindBySubjectId_WhenSubjectIdNotCached_ExpectToSearchLdapAndFindUser()
        {
            _authenticationService.Setup(m => m.FindUser(It.IsAny <string>()))
            .Returns(new OpenLdapAppUser {
                Username = "******"
            });

            var user = _inMemoryUserStore.FindBySubjectId("ldap_username");

            Assert.Equal("ldap_username", user.Username);
            _authenticationService.VerifyAll();
        }