I'm adding some unit tests for my ASP.NET Core Web API, and I'm wondering whether to unit test the controllers directly or through an HTTP client. Directly would look roughly like this:
[TestMethod]
public async Task GetGroups_Succeeds()
{
var controller = new GroupsController(
_groupsLoggerMock.Object,
_uowRunnerMock.Object,
_repoFactoryMock.Object
);
var groups = await controller.GetGroups();
Assert.IsNotNull(groups);
}
... whereas through an HTTP client would look roughly like this:
[TestMethod]
public void GetGroups_Succeeds()
{
HttpClient.Execute();
dynamic obj = JsonConvert.DeserializeObject<dynamic>(HttpClient.ResponseContent);
Assert.AreEqual(200, HttpClient.ResponseStatusCode);
Assert.AreEqual("OK", HttpClient.ResponseStatusMsg);
string groupid = obj[0].id;
string name = obj[0].name;
string usercount = obj[0].userCount;
string participantsjson = obj[0].participantsJson;
Assert.IsNotNull(name);
Assert.IsNotNull(usercount);
Assert.IsNotNull(participantsjson);
}
Searching online, it looks like both ways of testing an API seem to be used, but I'm wondering what the best practice is. The second method seems a bit better because it naively tests the actual JSON response from the Web API without knowing the actual response object type, but it's more difficult to inject mock repositories this way - the tests would have to connect to a separate local Web API server that itself was somehow configured to use mock objects... I think?
Edit: TL;DR
The conclusion you should do both because each test serves a different purpose.
Answer:
This is a good question, one I often ask myself.
First, you must look at the purpose of a unit test and the purpose of an integration test.
Unit Test :
Unit tests involve testing a part of an app in isolation from its
infrastructure and dependencies. When unit testing controller logic,
only the contents of a single action are tested, not the behaviour of
its dependencies or of the framework itself.
Things like filters, routing, and model binding will not work.
Integration Test :
Integration tests ensure that an app's components function correctly
at a level that includes the app's supporting infrastructures, such as
the database, file system, and network. ASP.NET Core supports
integration tests using a unit test framework with a test web host and
an in-memory test server.
Things like filters, routing, and model binding will work.
“Best practice” should be thought of as “Has value and makes sense”.
You should ask yourself Is there any value in writing the test, or am I just creating this test for the sake of writing a test?
Let's say your GetGroups() method looks like this.
[HttpGet]
[Authorize]
public async Task<ActionResult<Group>> GetGroups()
{
var groups = await _repository.ListAllAsync();
return Ok(groups);
}
There is no value in writing a unit test for it! because what you are doing is testing a mocked implementation of _repository! So what is the point of that?!
The method has no logic and the repository is only going to be exactly what you mocked it to be, nothing in the method suggests otherwise.
The Repository will have its own set of separate unit tests where you will cover the implementation of the repository methods.
Now let's say your GetGroups() method is more than just a wrapper for the _repository and has some logic in it.
[HttpGet]
[Authorize]
public async Task<ActionResult<Group>> GetGroups()
{
List<Group> groups;
if (HttpContext.User.IsInRole("Admin"))
groups = await _repository.FindByExpressionAsync(g => g.IsAdminGroup == true);
else
groups = await _repository.FindByExpressionAsync(g => g.IsAdminGroup == false);
//maybe some other logic that could determine a response with a different outcome...
return Ok(groups);
}
Now there is value in writing a unit test for the GetGroups() method because the outcome could change depending on the mocked HttpContext.User value.
Attributes like [Authorize] or [ServiceFilter(….)] will not be triggered in a unit test.
.
Writing integration tests is almost always worth it because you want to test what the process will do when it forms part of an actual application/system/process.
Ask yourself, is this being used by the application/system?
If yes, write an integration test because the outcome depends on a combination of circumstances and criteria.
Now even if your GetGroups() method is just a wrapper like in the first implementation, the _repository will point to an actual datastore, nothing is mocked!
So now, not only does the test cover the fact that the datastore has data (or not), it also relies on an actual connection being made, HttpContext being set up properly and whether serialisation of the information works as expected.
Things like filters, routing, and model binding will also work.
So if you had an attribute on your GetGroups() method, for example [Authorize] or [ServiceFilter(….)], it will be triggered as expected.
I use xUnit for testing so for a unit test on a controller I use this.
Controller Unit Test:
public class MyEntityControllerShould
{
private MyEntityController InitializeController(AppDbContext appDbContext)
{
var _controller = new MyEntityController (null, new MyEntityRepository(appDbContext));
var httpContext = new DefaultHttpContext();
var context = new ControllerContext(new ActionContext(httpContext, new RouteData(), new ActionDescriptor()));
_controller.ControllerContext = context;
return _controller;
}
[Fact]
public async Task Get_All_MyEntity_Records()
{
// Arrange
var _AppDbContext = AppDbContextMocker.GetAppDbContext(nameof(Get_All_MeetUp_Records));
var _controller = InitializeController(_AppDbContext);
//Act
var all = await _controller.GetAllValidEntities();
//Assert
Assert.True(all.Value.Count() > 0);
//clean up otherwise the other test will complain about key tracking.
await _AppDbContext.DisposeAsync();
}
}
The Context mocker used for unit testing.
public class AppDbContextMocker
{
/// <summary>
/// Get an In memory version of the app db context with some seeded data
/// </summary>
/// <param name="dbName"></param>
/// <returns></returns>
public static AppDbContext GetAppDbContext(string dbName)
{
//set up the options to use for this dbcontext
var options = new DbContextOptionsBuilder<AppDbContext>()
.UseInMemoryDatabase(dbName)
.Options;
var dbContext = new AppDbContext(options);
dbContext.SeedAppDbContext();
return dbContext;
}
}
The Seed extension.
public static class AppDbContextExtensions
{
public static void SeedAppDbContext(this AppDbContext appDbContext)
{
var myEnt = new MyEntity()
{
Id = 1,
SomeValue = "ABCD",
}
appDbContext.MyENtities.Add(myEnt);
//add more seed records etc....
appDbContext.SaveChanges();
//detach everything
foreach (var entity in appDbContext.ChangeTracker.Entries())
{
entity.State = EntityState.Detached;
}
}
}
and for Integration Testing: (this is some code from a tutorial, but I can't remember where I saw it, either youtube or Pluralsight)
setup for the TestFixture
public class TestFixture<TStatup> : IDisposable
{
/// <summary>
/// Get the application project path where the startup assembly lives
/// </summary>
string GetProjectPath(string projectRelativePath, Assembly startupAssembly)
{
var projectName = startupAssembly.GetName().Name;
var applicationBaseBath = AppContext.BaseDirectory;
var directoryInfo = new DirectoryInfo(applicationBaseBath);
do
{
directoryInfo = directoryInfo.Parent;
var projectDirectoryInfo = new DirectoryInfo(Path.Combine(directoryInfo.FullName, projectRelativePath));
if (projectDirectoryInfo.Exists)
{
if (new FileInfo(Path.Combine(projectDirectoryInfo.FullName, projectName, $"{projectName}.csproj")).Exists)
return Path.Combine(projectDirectoryInfo.FullName, projectName);
}
} while (directoryInfo.Parent != null);
throw new Exception($"Project root could not be located using application root {applicationBaseBath}");
}
/// <summary>
/// The temporary test server that will be used to host the controllers
/// </summary>
private TestServer _server;
/// <summary>
/// The client used to send information to the service host server
/// </summary>
public HttpClient HttpClient { get; }
public TestFixture() : this(Path.Combine(""))
{ }
protected TestFixture(string relativeTargetProjectParentDirectory)
{
var startupAssembly = typeof(TStatup).GetTypeInfo().Assembly;
var contentRoot = GetProjectPath(relativeTargetProjectParentDirectory, startupAssembly);
var configurationBuilder = new ConfigurationBuilder()
.SetBasePath(contentRoot)
.AddJsonFile("appsettings.json")
.AddJsonFile("appsettings.Development.json");
var webHostBuilder = new WebHostBuilder()
.UseContentRoot(contentRoot)
.ConfigureServices(InitializeServices)
.UseConfiguration(configurationBuilder.Build())
.UseEnvironment("Development")
.UseStartup(typeof(TStatup));
//create test instance of the server
_server = new TestServer(webHostBuilder);
//configure client
HttpClient = _server.CreateClient();
HttpClient.BaseAddress = new Uri("http://localhost:5005");
HttpClient.DefaultRequestHeaders.Accept.Clear();
HttpClient.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
}
/// <summary>
/// Initialize the services so that it matches the services used in the main API project
/// </summary>
protected virtual void InitializeServices(IServiceCollection services)
{
var startupAsembly = typeof(TStatup).GetTypeInfo().Assembly;
var manager = new ApplicationPartManager
{
ApplicationParts = {
new AssemblyPart(startupAsembly)
},
FeatureProviders = {
new ControllerFeatureProvider()
}
};
services.AddSingleton(manager);
}
/// <summary>
/// Dispose the Client and the Server
/// </summary>
public void Dispose()
{
HttpClient.Dispose();
_server.Dispose();
_ctx.Dispose();
}
AppDbContext _ctx = null;
public void SeedDataToContext()
{
if (_ctx == null)
{
_ctx = _server.Services.GetService<AppDbContext>();
if (_ctx != null)
_ctx.SeedAppDbContext();
}
}
}
and use it like this in the integration test.
public class MyEntityControllerShould : IClassFixture<TestFixture<MyEntityApp.Api.Startup>>
{
private HttpClient _HttpClient;
private const string _BaseRequestUri = "/api/myentities";
public MyEntityControllerShould(TestFixture<MyEntityApp.Api.Startup> fixture)
{
_HttpClient = fixture.HttpClient;
fixture.SeedDataToContext();
}
[Fact]
public async Task Get_GetAllValidEntities()
{
//arrange
var request = _BaseRequestUri;
//act
var response = await _HttpClient.GetAsync(request);
//assert
response.EnsureSuccessStatusCode(); //if exception is not thrown all is good
//convert the response content to expected result and test response
var result = await ContentHelper.ContentTo<IEnumerable<MyEntities>>(response.Content);
Assert.NotNull(result);
}
}
Added Edit:
In conclusion, you should do both, because each test serves a different purpose.
Looking at the other answers you will see that the consensus is to do both.
TL;DR
Is it best practice to test [...] directly or through an HTTP client?
Not "or" but "and". If you serious about best practices of testing - you need both tests.
First test is a unit test. But the second one is an integration test.
There is a common consensus (test pyramid) that you need more unit tests comparing to the number of integration tests. But you need both.
There are many reasons why you should prefer unit tests over integration tests, most of them boil down to the fact that unit test are small (in all senses) and integration tests - aren't. But the main 4 are:
Locality
When your unit test fails, usually, just from it's name you can figure out the place where the bug is. When integration test becomes red, you can't say right away where is the issue. Maybe it's in the controller.GetGroups or it's in the HttpClient, or there is some issue with the network.
Also, when you introduce a bug in your code it's quite possible that only one of unit tests will become red, while with integration tests there are more chances that more than one of them will fail.
Stability
With a small project which you can test on you local box you probably won't notice it. But on a big project with distributed infrastructure you will see blinking tests all the time. And that will become a problem. At some point you can find yourself not trusting test results anymore.
Speed
With a small project with a small number of tests you won't notice it. But on a bit project it will become a problem. (Network delays, IO delays, initialization, cleanup, etc., etc.)
Simplicity
You've noticed it yourself.
But that not always true. If you code is poorly structured, then it's easier to write integration tests. And that's one more reason why you should prefer unit tests. In some way they force you to write more modular code (and I'm not taking about Dependency Injection).
But also keep in mind that best practices are almost always about big projects. If your project is small, and will stay small, there are a big chance that you'll be better off with strictly opposite decisions.
Write more tests. (Again, that means - both). Become better at writing tests. Delete them latter.
Practice makes perfect.
If we limit the scope of discussion to Controller vs HttpClient testing comparison, I would say that it is better to use HttpClient. Because if you write tests for your controllers, you're already writing integration tests already and there is almost no point to write "weaker" integration tests while you can write stronger ones that is more realistic and also superset of the weaker ones.
For example, you can see from your own example that both of your test are testing exactly the same functionality. The different is that the latter one cover more area of testing -- JSON response, or can be something else like HTTP header you want to test. If you write the latter test, you don't need the first test at all.
I understand the pain of how to inject mocked dependencies. This requires more effort comparing to testing controller directly. However, .NET Core already provides a good set of tools to help you on that. You can setup the test host inside the test itself, configure it and get HttpClient from it. Then you can use that HttpClient for your testing purpose.
The other concern is that it is quite a tedious task to craft HttpClient's request for each test. Anyway, Refit can help you a lot on this. Refit's declarative syntax is quite easy to understand (and maintain eventually). While I would also recommend Refit for all remote API calls, it is also suitable for ASP.NET Core integration testing.
Combining all solutions available, I don't see why you should limit to controller test while you can go for more "real" integration test with only some little more effort.
I never have liked mocking in that as applications mature the effort spent on mocking can make for a ton of effort.
I like exercising endpoints by direct Http calls. Today there are fantastic tools like Cypress which allow the client requests to be intercepted and altered. The power of this feature along with easy Browser based GUI interaction blurs traditional test definitions because one test in Cypress can be all of these types Unit, Functional, Integration and E2E.
If an endpoint is bullet proof then error injection becomes impossible from outside. But even errors from within are easy to simulate. Run the same Cypress tests with Db down. Or inject intermittent network issue simulation from Cypress. This is mocking issues externally which is closer to a prod environment.
When doing unit test, it is important to know what are you going to test and write the tests based on your requirements. However, the second test, might looks like an integration test instead of an unit test, but I do not care to this point now!
Between your tests, I would recommend you to use the second option, because in the second unit test, you are testing your WebApi, as an WebApi, not as a class. For example suppose that you have a class with a method named X(). So how likely is it to write an unit test for it using Reflection? If it is completely unlikely, then writing an unit test based on Reflection is a waste of time. If it is likely, so you should write your test using Reflection too.
Moreover, using the second approach you are able to change the tech stack(For replace .Net with php) used for producing the WebApi, without changing you tests(This is what we expect from a WebApi too).
Finally, you should make a decision! how are you going to use this WebApi? How likely is it to call your WebApi using direct class instantiating?
Note:
It might be irrelevant to your question, but you should concentrate on your Asserts, too. For example asserting ResponseStatusCode and ResponseStatusMsg might not be needed and you can assert only one.
Or what will happen if obj is null? or obj has more than one member?
I'd say that they are not mutually exclusive. The first option is a classical unit test while the second is an integration test as involves more than a single unit of code.
If I had time to write either unit tests or integration tests, I'd pick unit tests as provides a more focused approach and gives, at least in my opinion, the best result from cost benefit.
In some particular projects where I had enough resources to write different suites of tests, I wrote both tests covering approaches. Where the second one would run without mocking anything (or maybe just the persistent storage) so I could test how all the components integrate together.
In relation to good practices, if you want to do real unit test, then you have no option but picking option one as no external dependencies are allowed (HttpClient is an external dependency).
Then, if the time and resources allow it, you could do integration testing for the most critical and/or complex paths.
If you are looking for some non programming You can use Postman, and can create collection of requests and can test multiple requests one by one.
You can use Swagger (aka OpenAPI).
Install Swashbuckle.AspNetCore from nuget.
using Microsoft.OpenApi.Models;
//in Startup.ConfigureServices
public void ConfigureServices(IServiceCollection services)
{
services.AddSwaggerGen(c =>
{
c.SwaggerDoc("v1", new OpenApiInfo { Title = "My API", Version = "v1" });
});
}
//in Startup.Configure
public void Configure(IApplicationBuilder app)
{
app.UseSwagger();
app.UseSwaggerUI(c =>
{
c.SwaggerEndpoint("/swagger/v1/swagger.json", "My API V1");
});
}
Finally, add "launchUrl": "swagger", in launchSettings.json
I used Dapper.Contrib in my Asp.Net Core Web API project.
I encountered a problem while writing a test with xUnit in this project.
For example, here is my method that adds records to my data layer.
public async Task<bool> AddAsync(User entity)
{
await using var connection = _dbConnection.CreateDbConnection();
await connection.OpenAsync();
return await connection.InsertAsync(entity) > 0;
}
My xUnit method that I try to write according to this method is below.
[Fact]
public void AddAsync_Should_Return_As_Expected()
{
var connection = new Mock<DbConnection>();
//Arrange
_userDbConnection.Setup(u => u.CreateDbConnection()).Returns(connection.Object);
//Act
var result = _sut.AddAsync(_user).GetAwaiter().GetResult();
//Assert
//Assert.Equal(result,actual);
}
When I run this test method, I get object not set error in
'return await connection.InsertAsync(entity) > 0;' line.
What exactly is my fault?
I believe what is happening is you are using a mocked connection and trying to call a Dapper method, InsertAsync, on it. The Dapper method is inevitably failing because it is not a real connection.
I'm not sure how much value you get using mocks here. What you really want to know, when testing AddAsync, is does it actually do what you want it to do which is insert data into the database. So if I were you I would turn this test into an integration test by using a real connection instead of a mocked one. One way of doing this is to
Use a test database for the purposes of testing
Before running the test delete all data from the test database
In your assert use Dapper or otherwise to check that a query for the entity brings back the data you expect to be in the database.
I don't necessarily recommend this but another approach could be to use an in memory database. See for example unit testing Dapper Repositories.
Ive written a couple of unit tests while using dependency injection and the httpClient in the .net Core 2.0 framework.
Ive been testing my controllers like this:
var result = await __client.PostAsync("api/production-line/validate-assignment-deadline", null);
But now i wanted to mock an object and after searching a bit on the internet all i could find was to do it like this:
var controller = new ProductionLineController(mockProductionLineProvider);
which is not testing the routing and on top of that i would have to create a lot of objects. so i dont want mock my object in this way.
I would like to be able to replace the service with an mock object i havent found a way to get the IServiceCollection into my unittest method.
I would like to be able to do something like this:
var mockingDate = new DateTime(date.Year, date.Month, date.Day, 12, 00, 00);
__constantsMock.Setup(x => x.GetCurrentDateTime()).Returns(mockingDate);
services.Replace(new ServiceDescriptor(typeof(IConstants), ConstantsMock.Object));
var result = await __client.PostAsync("api/production-line/validate-assignment-deadline", null);
I hope you can help me think of ways to get to a solution that doesnt involve me having to create every object that i would inject normaly.
Thank you in advance
edit:
im indeed doing integration tests, i want to test everything but i need to be able to configure the result coming from a DateTime.Now so i made the constants class with a function to return the datetime.now and im trying to mock/stub the class/function. that way i can test multiple scenario's that could occur.
You are looking at the standard way of mocking; you create stubs for all the dependencies (you need to be able to control all of them!) and create the controller. Being able to mock the DI framework wouldn't really buy you anything; you would still need to provide all the dependencies to the class when you constructed it.
Use mocking libraries like NSubstitute to make it easier; if you feel like you have too many dependencies then I would suspect you need to refactor your design (perhaps that controller does too much).
Note that testing with actual HTTP requests is more of an integration test; you are testing the whole app instead of just one class. In that case you can set up different environments for your program and have one that will set up the injector with whatever extra mocks/test data you need.
Once you start doing something like issuing a request to an action, you're pretty much well outside of unit test territory. What you're doing here is integration testing.
As long as you're doing integration testing, you might as well use TestServer, which will actually give you a much more accurate platform for integration tests. Setting up all the dependencies manually doesn't do anything for you in ensuring that your application actually functions as it should. The full documentation is here, but basically, you just do:
_server = new TestServer(new WebHostBuilder()
.UseStartup<Startup>());
_client = _server.CreateClient();
The return of _server.CreateClient() is actually an instance of HttpClient, so your actual test code doesn't really need to change. However, now you've got a full mockup of all your services and config baked in.
The solution to my problem was as follows:
Make an extra starting class that inherits from your StartUp class
Give that class the following code:
public class UnitTestStartup : Startup
{
public static IServiceProvider ServiceProvider;
public static IServiceCollection Services;
public static Mock<IConstants> ConstantsMock;
public void ConfigureTestingServices(IServiceCollection services)
{
ServiceProvider = base.ConfigureServices(services);
Services = services;
ConstantsMock = new Mock<IConstants>();
services.Replace(new ServiceDescriptor(typeof(IConstants), ConstantsMock.Object));
}
}
Make the ConstantsMock (the service you want to mock) available in your baseclass
Like this:
protected Mock<IConstants> __constantsMock;
__constantsMock = UnitTestStartup.ConstantsMock;
have every unit test class inherit from your baseclass
override the __constantsMock with a new object and you're done
I have MVC web app that uses EntityFramework context and it stores it in HttpContext.Current.Items. When HttpContext.Current isn't available then it uses CallContext.SetData to store data in current thread storage. HttpContext is used for web app itself and CallContext is used in unit tests to store the same EF DbContext there.
We are also trying to use async\await as we have library that relays a lot on them, and it works great in web app. But it fails in unit tests as CallContext.SetData isn't restored after thread returns to await block.
Here is simplified sample of the issue:
public async Task Test()
{
ContextUtils.DbContext = new SomeDbContext();
using (ContextUtils.DbContext){
await DoSomeActions();
}
}
public async Task DoSomeActions(){
var data = await new HttpClient().GetAsync(somePage);
// on next line code would fail as ContextUtils.DbContext is null
// as it wasn't synced to new thread that took it
var dbData = ContextUtils.DbContext.SomeTable.First(...);
}
So in that example ContextUtils.DbContext basically sets HttpContext\CallContext.SetData. And it works fine for web app, and fails in unit test as SetData isn't shared and on ContextUtils.DbContext.SomeTable.First(...); line DbContext is null.
I know that we can use CallContext.LogicalSetData\LogicalGetData and it would be shared withing ExecutionContext, but it requires item to be Serializable and i don't want to mark DbContext with serialization attribute as would try to serialize it.
I also saw Stephen's AsyncEx library (https://github.com/StephenCleary/AsyncEx) that has own SynchronizationContext, but it would require me to update my code and use AsyncContext.Run instead of Task.Run, and i'm trying to avoid code updating just for unit tests.
Is there any way to fix it without changing the code itself just to make it work for unit tests? And where EF DbContext should be stored in unit tests without passing it as parameter and to be able to use async\await?
Thanks
OK, there's a lot of things here.
Personally, I would look askance at the use of CallContext.GetData as a fallback to HttpContext.Current, especially since your code makes use of async. Consider using AsyncLocal<T> instead. However, it's possible that AsyncLocal<T> may also require serialization.
I also saw Stephen's AsyncEx library (https://github.com/StephenCleary/AsyncEx) that has own SynchronizationContext, but it would require me to update my code and use AsyncContext.Run instead of Task.Run, and i'm trying to avoid code updating just for unit tests.
A couple of things here:
You shouldn't be using Task.Run on ASP.NET in the first place.
Using Task.Run will prevent the (non-logical) call context from working, as well as HttpContext.Current. So I assume that your code is not accessing the DbContext from within the Task.Run code.
It sounds like your best option is to use my AsyncContext. This class was originally written for asynchronous unit tests (back before unit test frameworks supported asynchronous unit tests). You shouldn't need to update your code at all; just use it in your unit tests:
public void Test()
{
AsyncContext.Run(async () =>
{
ContextUtils.DbContext = new SomeDbContext();
using (ContextUtils.DbContext)
{
await DoSomeActions();
}
});
}
Avoid using async void. Make the test method await-able by used Task
[TestMethod]
public async Task Test() {
ContextUtils.DbContext = new SomeDbContext();
using (ContextUtils.DbContext) {
await DoSomeActions();
}
}
HttpContext is not available during unit test as it is tied to IIS which is not present during unit tests. Avoid tightly coupling your code to HttpContext treat it like a 3rd party resource and abstract it away behind code you can control. It will make testing maintaining and testing your code easier. Consider reviewing your current design.
I can't test any logoff, login, register action from AccountController with the new Microsoft Fake Framework without having this error message: System.Security.VerificationException: Operation could destabilize the runtime.
The unit test is real simple:
[TestMethod]
public void LogOff()
{
var AccountController = new AccountController();
RedirectToRouteResult RedirectToRouteResult;
//Scope the detours we're creating
using (ShimsContext.Create())
{
ShimWebSecurity.Logout = () => { };
var test = AccountController.LogOff();
RedirectToRouteResult = AccountController.LogOff() as RedirectToRouteResult;
}
Assert.IsNotNull(RedirectToRouteResult);
Assert.AreEqual("Index", RedirectToRouteResult.RouteValues["Action"]);
Assert.AreEqual("Home", RedirectToRouteResult.RouteValues["controller"]);
}
Also find this: http://social.msdn.microsoft.com/Forums/en-US/vsunittest/thread/f84962ea-a9b2-4e0d-873b-e3cf8cfb37e2 that talk about the same bug but no answer.
Thanks!
I asked the same question before VS2012 Update 1 was released (VerificationException when instantiating MVC controller during unit testing) and I got the response from a guy from Microsoft who said that they are working on it and it should be available in the next update. Well, nothing since then.
However, in order to get the result and to continue testing using Microsoft Fakes Framework, I wrapped the calls to MVC methods like those in the UrlHelper class with my own private methods that return primitive types like string and then Shim the unit test to give me a desired result. That way I never made a call to the underlying MVC infrastructure and I got the desired result. Also, you will need to remove System.Web.Mvc.Fakes reference otherwise VerificationException will keep popping up.
If you find this tedious then you should switch to a more mature unit testing framework like Moq or Rhino.