Tricky continuous testing and self hosting WebAPI issue...

When using WebAPI inside a test fixture make sure you shutdown the HttpSelfHostServer instance correctly or your tests will more than likely fail when run from a continuous testing framework like nCrunch.

See this post for info about using the self hosting version of WebAPI inside a test fixture.

So my tests were running successfully when run inside Visual Studio from either the inbuilt runner or via Reshaper, but were failing when run from nCrunch:

The failing tests weren't consistent either, sometimes none would fail, sometimes a couple, sometimes all...

What the tests had in common was they were using a shared resource setup inside the test fixture setup method - this is like the setup method for a test but scoped at the class (test fixture) level. The setup was failing randomly were it was setting up the WebAPI self host - see highlighted yellow area, you can see the failing icon for nCrunch at the side:

The exception was telling me it was trying to create an instance of the service on a port already assigned:

So my first thought was because the tests for the fixture are being run in parallel then multiple instances of the fixture are trying to be created at the same time and therefore multiple registration attempts for the same port...

But after debugging the code with breakpoints for the SetUp & TearDown it appears this was wrong, these methods were only called once per run. This meant the service wasn't shutting down correctly when test execution had completed.

The TestService class is shown below. I thought I was shutting down the WebAPI host correctly by calling Dispose in the class Dispose method:

   1:  public class TestService : IDisposable

   2:  {

   3:      private readonly string _baseUrl;

   4:   

   5:      private HttpSelfHostServer _server;

   6:   

   7:      public IList<Employee> Employees;

   8:      public IList<Report> Reports;

   9:      public TimeSpan Delay;

  10:   

  11:      public TestService(string baseUrl)

  12:      {

  13:          _baseUrl = baseUrl;

  14:   

  15:          SetUpControllers();

  16:          SetUpHost();

  17:      }

  18:   

  19:      public void Dispose()

  20:      {

  21:          _server.Dispose();

  22:      }

  23:   

  24:      private void SetUpHost()

  25:      {

  26:          var config = new HttpSelfHostConfiguration(_baseUrl);

  27:   

  28:          config.Routes.MapHttpRoute("DefaultAPI", "api/{controller}/{id}", new { id = RouteParameter.Optional });

  29:   

  30:          _server = new HttpSelfHostServer(config);

  31:          _server.OpenAsync().Wait();

  32:      }

  33:   

  34:      private void SetUpControllers()

  35:      {

  36:          Employees = new List<Employee>

  37:          {  

  38:              new Employee { Id = 1, FirstName = "Ollie", LastName = "Riches" },

  39:              new Employee { Id = 2, FirstName = "Steve", LastName = "Austin" },

  40:          };

  41:   

  42:          EmployeesController.Employees = Employees;

  43:   

  44:          Delay = TimeSpan.FromSeconds(3);

  45:          Reports = new List<Report>

  46:          {  

  47:              new Report { Id = 1, Name = "SlowReport" }

  48:          };

  49:   

  50:          ReportsController.Delay = Delay;

  51:          ReportsController.Reports = Reports;

  52:      }

  53:  }

But this wasn't the case, after changing to the following all tests were passing as expected:

   1:  public void Dispose()

   2:  {

   3:      _server.CloseAsync().Wait();

   4:      _server.Dispose();

   5:  }

I had to re-initialising nCrunch to force any remaining service instances to shutdown:

I would have thought calling Dispose on HttpSelfHostServer would have meant it blocked until the server had shutdown but it appears not. Looking into the implementation it appears it doesn't close the server unless a task completion source had already been defined (also shown is the implementation for CloseAsync()):

I hope this helps if you run into this issue :)