Integration testing with TestContainers & AppFixture

AppFixture.cs

using Testcontainers.MongoDb;

public class Sut : AppFixture<Program>
{
    const string Database = "TestingDB";
    const string RootUsername = "root";
    const string RootPassword = "password";

    MongoDbContainer _container = null!;

    protected override async Task PreSetupAsync()
    {
        //this function is only ever called once before the WAF/SUT instance is created & cached.
        //every derived AppFixture type will cache just one instance of a WAF/SUT.
        //more info: https://fast-endpoints.com/docs/integration-unit-testing#app-fixture

        _container = new MongoDbBuilder()
                     .WithImage("mongo")
                     .WithUsername(RootUsername)
                     .WithPassword(RootPassword)
                     .WithCommand("mongod")
                     .Build();
        await _container.StartAsync();
    }

    protected override void ConfigureApp(IWebHostBuilder b)
    {
        b.ConfigureAppConfiguration(
            c =>
            {
                c.AddInMemoryCollection(
                    new Dictionary<string, string?>
                    {
                        { "Mongo:Host", _container.Hostname },
                        { "Mongo:Port", _container.GetMappedPublicPort(27017).ToString() },
                        { "Mongo:DbName", Database },
                        { "Mongo:UserName", RootUsername },
                        { "Mongo:Password", RootPassword }
                    });
            });
    }

    protected override async Task TearDownAsync()
    {
        //await _container.DisposeAsync();
        //NOTE: there's no need to dispose the container here as it will be automatically disposed by testcontainers pkg when the test run finishes.
        //      this is especially true if this AppFixture is used by many test-classes with WAF caching enabled.
        //      so, in general - containers don't need to be explicitly disposed, unless you disable WAF caching.
    }
}