I want to perform integration tests which involve interaction with service bus. I have noticed that some messages are not sent, even though no exception gets thrown. I am using a free tier of ASB.

That's the service method responsible for sending the message:

    public class ServiceBusMessagingSender<T> : IMessagingSender<T> where T : IMessage
    {

    private readonly string _connectionString = Environment.GetEnvironmentVariable("SERVICE_BUS_CONNECTION_STRING_SENDER");
    private readonly ServiceBusSender _sender;
    private readonly IMessageSerializer<T> _messageSerializer;

    public ServiceBusMessagingSender(string queueName, IMessageSerializer<T> messageSerializer, string connectionString=null)
    {
        _messageSerializer = messageSerializer;
        _connectionString ??= connectionString;
        var client = new ServiceBusClient(_connectionString);
        this._sender = client.CreateSender(queueName);
    }


    public void SendMessage(T message)
    {
        var serviceBusMessage = _messageSerializer.Serialize(message);
        _sender.SendMessageAsync(serviceBusMessage).GetAwaiter().GetResult();
    }

This method is then called in tests in NUnit suite:

    public class EndtoEndTests {

    private readonly ServiceBusMessagingSender<DataRequestDto> _messagingSender = new(RequestsQueue, new MessageSerializer<DataRequestDto>(), WriterConnectionString);


    [Test]
    public void GoodTypes()
    {
        //...
        
        //WHEN
        var request = new GoodTypesRequest()
        {
            RequestTimeStamp = DateTime.Now,
            RequestType = RequestType.GoodTypes
        };

        _messagingSender.SendMessage(request );
        ///...
    }
}

I am using the following versions of packages for ASB:

    <PackageReference Include="Azure.Messaging.ServiceBus" Version="7.2.0" />
    <PackageReference Include="Microsoft.Azure.ServiceBus" Version="5.1.3" />