public void TestAddToRole_ShouldCallUserManagerAddToRole(string userId, string role)
{
//Arrange
var mockedUserStore = new Mock <IUserStore <User> >();
var mockedUserManager = new Mock <ApplicationUserManager>(mockedUserStore.Object);
var mockedHttpContextProvider = new Mock <IHttpContextProvider>();
mockedHttpContextProvider.Setup(p => p.GetUserManager <ApplicationUserManager>()).Returns(mockedUserManager.Object);
var provider = new AuthenticationProvider(mockedHttpContextProvider.Object);
//Act
provider.AddToRole(userId, role);
//Assert
mockedUserManager.Verify(m => m.AddToRoleAsync(userId, role), Times.Once);
}