In essence, I have an Aspire project like below, where the backend is a web server.

var builder = DistributedApplication.CreateBuilder(args);

var saPassword = builder.AddParameter("sa-password");

var database = builder.AddSqlServer("sql-for-tests")
    .WithContainerName("sql-for-tests")
    .WithPassword(saPassword)
    .AddDatabase("TestDatabase");

var backend = builder.AddProject<Projects.Backend>("backend")
    .WithReference(database)
    .WaitFor(database);

var app = builder.Build();

app.Run();

For this server I would like like to run integration tests, so I create a test project and use the DistributedApplicationTestingBuilder. Running dotnet test on my local machine (WSL) works just like expected: the database is set up, the backend can connect to it, and a basic integration test can call the backend and get a result.

Now, running locally is all good and well but then I also want to run this in my company's CI enviroment, which is Gitlab where each pipeline is run inside a container (with an image of my choosing). This is where I get issues, and the dotnet test fails with the following:

fail: Aspire.Hosting.Dcp.dcpctrl.ServiceReconciler.Proxy[0]
      Error handling TCP connection	{"Service": {"name":"sql-for-tests"}, "error": "Could not establish TCP connection to endpoint: dial tcp 127.0.0.1:32774: connect: connection refused\ncontext canceled"}

This makes sense, as the CI environment would run the dotnet test inside my specified container but the SQL container is not run inside that container but next to it. As such, there is nothing on localhost listening to the port.

Is there a way to get this scenario working? I guess what I am looking for is a way to tell Aspire that SQL is not really running on localhost, but should kind of be regarded as an external resource. Or any sort of guidance if this is a dead end or not.

I think this might be the same question as in #6567, but that one died off.