C#•12mo ago

How to test this code?

I am trying to refactor some code in a background service that looks like this:

public class MyBackgroundService : BackgroundService {
    public MyBackgroundService(IKafkaConsumer consumer, IOptionMonithor<WorkerConfig> config, NotificationSender sender) 
    {
        _consumer = consumer;
        _config = config;
        _sender = sender;
    }

    protected override async Task ExecuteAsync(CancellationToken stoppingToken) 
    {
        while(!stoppingToken.IsCancellationRequested) 
        {
            await ConsumeKafkaAndSendNotificationAsync();
            await Task.Delay(TimeSpan.FromMilliseconds(_config.CurrentValue.Delay), stoppingToken);
        }
    }
    
    private async Task ConsumeKafkaAndSendNotificationAsyncc()
    {
        var timer = new StopWatch();
        timer.Start();
        Message? message;
        do 
        {
           message  = _consumer.ConsumeMessage(); 
          // .....
          // do some work here on the message
          // .....
           await _sender.SendNotificationAsync(message);
        } while (
            message != null && timer.Elapsed < TimeSpan.FromMilliseconds(_config.CurrentValue.Delay)
        )
    }
}

public class MyBackgroundService : BackgroundService {
    public MyBackgroundService(IKafkaConsumer consumer, IOptionMonithor<WorkerConfig> config, NotificationSender sender) 
    {
        _consumer = consumer;
        _config = config;
        _sender = sender;
    }

    protected override async Task ExecuteAsync(CancellationToken stoppingToken) 
    {
        while(!stoppingToken.IsCancellationRequested) 
        {
            await ConsumeKafkaAndSendNotificationAsync();
            await Task.Delay(TimeSpan.FromMilliseconds(_config.CurrentValue.Delay), stoppingToken);
        }
    }
    
    private async Task ConsumeKafkaAndSendNotificationAsyncc()
    {
        var timer = new StopWatch();
        timer.Start();
        Message? message;
        do 
        {
           message  = _consumer.ConsumeMessage(); 
          // .....
          // do some work here on the message
          // .....
           await _sender.SendNotificationAsync(message);
        } while (
            message != null && timer.Elapsed < TimeSpan.FromMilliseconds(_config.CurrentValue.Delay)
        )
    }
}

Complex work should usually be kept somewhere else outside of the loop of the backgroundService. However, things get hairy enough that some tests will help.

2 Replies

LazyGuardOP•12mo ago

To test the code, II mocked the consumer and i have a lot of tests like this

[Fact]
public async Task Should_Assert_That_Some_Work_Is_Done()
{
    // Arrange
    var message = new Mesagge(...);
    MockedConsumer.ConsumeMessage().ReturnsForAnyArgs(x =>message, x =>null));

    Notification? sentNotification = null;
    MockedSender.SendNotificationAsync(Arg.Do<Notification>(x => sentNotification = x)).Returns(Task.CompletedTask);

    // Act
    Task.Delay(Configuration.Delay + 100).Wait();

    //Assert
    // Some assertions on the work being done
    Assert.NotNull(sentNotification?.Message?.Price); 
    
}

[Fact]
public async Task Should_Assert_That_Some_Work_Is_Done()
{
    // Arrange
    var message = new Mesagge(...);
    MockedConsumer.ConsumeMessage().ReturnsForAnyArgs(x =>message, x =>null));

    Notification? sentNotification = null;
    MockedSender.SendNotificationAsync(Arg.Do<Notification>(x => sentNotification = x)).Returns(Task.CompletedTask);

    // Act
    Task.Delay(Configuration.Delay + 100).Wait();

    //Assert
    // Some assertions on the work being done
    Assert.NotNull(sentNotification?.Message?.Price); 
    
}

When I launch tests, the majority fail and I am trying to wrap my head around and understand why. When Launching tests individually, they all pass ! Observations: 1. Some tests fail with a null value when a non null value is expected 2. Some tests fail with a value that is not null but different from the expected. Any help ? 🤔

phaseshift•12mo ago

Is MockedSender static or part of a fixture? If you want to wait until a message is received in a mock then use some form of barrier like ManualResetEvent (instead of doing an arbitrary wait, which btw is not the 'Act' of the test)

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How to test this code?