Unit Test a Time Triggered Azure Function

Question

I've got a time-triggered Azure Function which I want to test with XUnit and MOQ.

While I know I need to call the Run method of the class using an instance of the class say funTimeTriggeredObj where

funTimeTriggered funTimeTriggeredObj = new funTimeTriggered(queueSchedulerMock.Object, telemetryHelperMock.Object)

like

funTimeTriggeredObj.Run(param1, param2, loggerMock.Object)

where

private Mock loggerMock = new Mock()

I'm not sure how should I mock the param1 & param2 which are TimerInfo and ExecutionContext objects respectively.

The reason why I'm asking is because neither 'TimerInfo' nor 'ExecutionContext' implements any interface which can be mocked.

Below is my actual function implementation. Any help whatsoever would be highly appreciated.

using System;
using System.Threading.Tasks;
using Microsoft.Azure.WebJobs;
using Microsoft.Extensions.Logging;

public  class funTimeTriggered
{
    private  string  _invocationID;
    private readonly IQueueScheduler _queueScheduler;
    private readonly ITelemetryHelper _telemetryHelper;

    public funTimeTriggered(IQueueScheduler queueScheduler, ITelemetryHelper telemetryHelper)
    {
        _queueScheduler = queueScheduler;
        _telemetryHelper = telemetryHelper;
    }

    [FunctionName("funTimeTriggered")]
    public  async Task Run([TimerTrigger("0/10 * * * * *")]TimerInfo myTimer, ExecutionContext context, ILogger log)
    {
        log.LogInformation($"C# Timer trigger function executed at: {DateTime.Now}");
        try
        {
            _invocationID = context.InvocationId.ToString();
            await _queueScheduler.SendEventsToServiceBusAndDeleteFromSQS();
        }
        catch (Exception ex)
        {
            log.LogError(ex.Message);
            _telemetryHelper.LogException(ex);
            throw ex;
        }
    }
}

user_5233410 · Answer

If there are no undesired effects of using actual instance of those classes and you can actually initialize them then create actual instance and pass them to the function under test.

They do not have to be interfaces or mocked if using the actual instance(s) has no unwanted effects

//Arrange

//...omitted for brevity

var param1 = new TimerInfo(...); 
var param2 = = new ExecutionContext {
    InvocationId = Guid.NewGuid()
};

//Act
await funTimeTriggeredObj.Run(param1, param2, loggerMock.Object);

//Assert
//...assert expected behavior

And since in this test case the timer is not even used by the function, it can be ignored altogether

//Arrange

//...omitted for brevity

var param1 = default(TimerInfo); //null
var param2 = = new ExecutionContext {
    InvocationId = Guid.NewGuid()
};

//Act
await funTimeTriggeredObj.Run(param1, param2, loggerMock.Object);

//Assert
//...assert expected behavior

user_1882699 · Answer

You could put the logic of your Azure function into a separate class and write unit tests for that class.

What could be done is an integration test, if there was a another function created with a different trigger (for example HTTP), doing the same thing.

user_7806334 · Answer

The setup is right. But instead of trying to mock TimerInfo and ExecutionContext, or implementing them, you can simply send null since you don't use them inside your function.

user_4549327 · Answer

I had similar tests that I needed to do. I used FakeItEasy though, but I'm hoping this will help you (or others) nonetheless.

Packages used:

Some tests:

public class FunTimeTriggeredConstructorTests
{
    private ITelemetryHelper _fakeITelemetryHelper;
    private IQueueScheduler _fakeIQueueScheduler;

    public FunTimeTriggeredConstructorTests()
    {
        _fakeITelemetryHelper= A.Fake();
        _fakeIQueueScheduler = A.Fake();
    }

    [Fact]
    public void ShouldThrow_ArgumentNullException_When_IQueueScheduler_Is_Null()
    {
        _fakeIQueueScheduler = null;

        Assert.Throws(() => new FunTimeTriggered(_fakeITelemetryHelper, _fakeIQueueScheduler));
    }
}

public class RunTests
{
    private ITelemetryHelper _fakeITelemetryHelper;
    private IQueueScheduler _fakeIQueueScheduler;
    private TimerInfo _fakeTimerInfo;
    private ExecutionContext _fakeExecutionContext;
    private ILogger _fakeILogger;
    private FunTimeTriggered _funTimeTriggered;

    public RunTests()
    {
        _fakeITelemetryHelper= A.Fake();
        _fakeTimerInfo = A.Fake();
        _fakeIQueueScheduler = A.Fake();
        _fakeExecutionContext = A.Fake();
        _fakeILogger = A.Fake();

        _funTimeTriggered = new FunTimeTriggered(_fakeITelemetryHelper, _fakeIQueueScheduler);
    }

    [Fact]
    public async Task ShouldCall_IQueueScheduler_SendEventsToServiceBusAndDeleteFromSQS_AtMost_Once()
    {
        A.CallTo(() => _fakeExecutionContext.InvocationId).Returns("");

        await FunTimeTriggered.Run(_fakeTimerInfo, _fakeExecutionContext, _fakeILogger);

        A.CallTo(() => _queueScheduler.SendEventsToServiceBusAndDeleteFromSQS()).MustHaveHappenedOnceExactly();
    }
}

user_8005350 · Answer

 // Arrange
 TimerSchedule schedule = new DailySchedule("2:00:00");
 TimerInfo timerInfo = new TimerInfo(schedule, It.IsAny(), false);
    
 // Act
 await _functions.TimerTrigerFunction(timerInfo, _durableOrchestrationClient.Object, _log.Object);

Unit Test a Time Triggered Azure Function

5 Answers