TaskCanceledException thrown at the end of NUnit test

[paulhunttech]

I am using all the latest packages and am trying to write my first Aspire test with NUnit. The test itself passes but if I debug it builder.Build().Run() throws a TaskCancelled exception.

I don't get this exception if I debug the Aspire project normally so I'm assuming it must be something to do with my test setup. Unfortunately the exception gives me very little information to go on.

Does anyone have ideas how I can get more detail about the problem?

The exception:

System.AggregateException
  HResult=0x80131500
  Message=One or more errors occurred. (A task was canceled.)
  Source=System.Private.CoreLib
  StackTrace:
   at System.Threading.Tasks.Task.ThrowIfExceptional(Boolean includeTaskCanceledExceptions)
   at System.Threading.Tasks.Task.Wait(Int32 millisecondsTimeout, CancellationToken cancellationToken)
   at System.Threading.Tasks.Task.Wait()
   at Aspire.Hosting.DistributedApplication.Run()
   at Program.<Main>$(String[] args) in D:\Honest\src\Honest.AppHost\Program.cs:line 113

Inner Exception 1:
TaskCanceledException: A task was canceled.

The test:

[Test]
public async Task CheckHealth()
{
    // Arrange
    var builder = await DistributedApplicationTestingBuilder.CreateAsync<Projects.Honest_AppHost>();

    builder.Services.AddLogging(logging =>
    {
        logging.ClearProviders();
        logging.AddSimpleConsole();
        logging.SetMinimumLevel(LogLevel.Trace);
        logging.AddFilter("Aspire", LogLevel.Trace);
        logging.AddFilter(builder.Environment.ApplicationName, LogLevel.Trace);
    });

    await using var application = await builder.BuildAsync();
    await application.StartAsync();
    
    // Act
    var httpClient = application.CreateHttpClient("admin-site");
    await application.ResourceNotifications.WaitForResourceHealthyAsync("admin-site");
    var response = await httpClient.GetAsync("/health");

    // Assert
    Assert.That(response.StatusCode, Is.EqualTo(HttpStatusCode.OK));
}

[engineering87]

Hello @paulhunttech,
TaskCanceledException happens because builder.Build().Run() blocks until shutdown, which doesn't work in a test runner context, the task gets canceled when the test ends.
Since you're already using DistributedApplicationTestingBuilder, stick with BuildAsync() + StartAsync() (as in your test) instead of Run(). That’s the supported way to run Aspire apps in tests.