Mocking - cannot instantiate proxy class of property?

Question

Inside my tests, here is my code:

[SetUp]
public void Initialise()
{
    mockOwinManager = new Mock<IOwinManager<ApplicationUser, ApplicationRole>>();
    mockSearch = new Mock<ISearch<ApplicationUser>>();
    mockMail = new Mock<IRpdbMail>();
    mockUserStore = new Mock<IUserStore<ApplicationUser>>();

    mockOwinManager.Setup(x => x.UserManager).Returns(() => new AppUserManager(mockUserStore.Object));

    sut = new UsersController(mockOwinManager.Object, mockSearch.Object, mockMail.Object);
}

And then the test itself:

[Test]
public void WhenPut_IfUserIsNullReturnInternalServerError()
{
    //Arrange
    mockOwinManager.Setup(x => x.UserManager.FindByIdAsync(It.IsAny<string>())).Returns(() => null);

    //Act
    var response = sut.Put(new AppPersonUpdate());

    //Assert
    Assert.AreEqual(response.Result.StatusCode, HttpStatusCode.InternalServerError);
}

But my arrange line throws the following error:

Can not instantiate proxy of class: Microsoft.AspNet.Identity.UserManager`1[[SWDB.BusinessLayer.Identity.ApplicationUser, SWDB.BusinessLayer, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]]. Could not find a parameterless constructor.

Why is this so, since in Setup I've set my mockOwinManager's UserManager property in what I'd like it to return already?

Answer 1

Create a mock object of UserManager first. Then setup its virtual method FindByIdAsync(given that the type of the property UserManager is a class AppUserManager and lets say this class implements IAppUserManager).

var yourMockOfUserManager = new Mock<IAppUserManager>();
yourMockOfUserManage.Setup(x=>x.FindByIdAsync(It.IsAny<string>())).Returns(() => null);

and finally

mockOwinManager.Setup(x => x.UserManager).Returns(() => yourMockOfUserManager.Object);

Answer 2

UserManager class accepts IUserStore<ApplicationUser> in a constructor, which is used to get an access to FindByIdAsync and etc

When I need to test classes which require UserManager, I do mock for IUserStore and setup its FindByIdAsync method, then I create an instance of UserManager and provide my mock into its parameters. This is a class constructor which requires UserManager:

internal class UserManagerWrapper
{
    private readonly IEditUserResponceDataModelProvider _editUserResponceDataModelProvider;
    private readonly UserManager<User> _userManager;
    private readonly IUserModelFactory _userModelFactory;

    public UserManagerWrapper(UserManager<User> userManager,
        IUserModelFactory userModelFactory,
        IEditUserResponceDataModelProvider editUserResponceDataModelProvider)
    {
        _userManager = userManager;
        _userModelFactory = userModelFactory;
        _editUserResponceDataModelProvider = editUserResponceDataModelProvider;
    }

    public async Task<IUserModel> FindByIdAsync(string id)
    {      
        var user = await _userManager.FindByIdAsync(id);
        return _userModelFactory.Create(user.Id, user.Email, user.Year, user.UserName);
    }
}

This is my test for UserManagerWrapper:

private Mock<IUserStore<User>> UserStoreMock { get; set; }

[SetUp]
public void SetUp()
{
    UserStoreMock = new Mock<IUserStore<User>>();
    UserStoreMock.Setup(x => x.FindByIdAsync(It.IsAny<string>(), CancellationToken.None))
        .Returns(Task.FromResult(new User() {Year = 2020}));
}

[TestCase(2020)]
public async Task ValidateUserYear(int year)
{

    var userManager = new UserManager<User>(UserStoreMock.Object, null, null, null, null, null, null, null, null);

    var userManagerWrapper = new UserManagerWrapper(userManager, new UserModelFactory(), null);
    var findByIdAsync = await userManagerWrapper.FindByIdAsync("1");
    Assert.AreEqual(findByIdAsync.Year, year);
}`: