Unit test Azure Event Hub Trigger (Azure Function)

I have an Azure Function which is an EventHub Trigger. The events are being processed in a batch EventData[].

[FunctionName("EventHubTriggerCSharp")]
public async Task Run([EventHubTrigger("samples-workitems", Connection = "EventHubConnectionAppSetting")] EventData[] eventHubMessages, ILogger log)
{
    foreach (var message in eventHubMessages)
    {
        log.LogInformation($"C# function triggered to process a message: {Encoding.UTF8.GetString(message.Body)}");
        log.LogInformation($"EnqueuedTimeUtc={message.SystemProperties.EnqueuedTimeUtc}");
        await service.CallAsync(message);
    }
}

How can one unit test a Function that requires a EventData[] as the payload?

You should be able to construct the array of EventData and pass that to the Run method along with a mock logger instance.

I have used MsTest but it should be the same logic with NUnit.

[TestClass]
public class EventHubTriggerCSharpTests
{
    private readonly Mock<IService> _mockService = new Mock<IService>();
    private readonly Mock<ILogger> _mockLogger = new Mock<ILogger>();

    private EventHubTriggerCSharp _eventHubTriggerCSharp;

    [TestInitialize]
    public void Initialize()
    {
        _eventHubTriggerCSharp = new EventHubTriggerCSharp(_mockService.Object);
    }

    [TestMethod]
    public async Task WhenEventHubTriggersFunction_ThenCallAsyncWithEventHubMessage()
    {
        // arrange
        var data = "some data";

        var eventHubMessages = new List<EventData>
        {
            new EventData(Encoding.UTF8.GetBytes(data))
            {
                SystemProperties = new EventData.SystemPropertiesCollection(1, DateTime.Now, "offset", "partitionKey")
            }
        };

        // act
        await _eventHubTriggerCSharp.Run(eventHubMessages.ToArray(), _mockLogger.Object);

        // assert
        _mockService.Verify(x => x.CallAsync(eventHubMessages[0]));
    }
}

Note: I haven't actually run the test due to an issue with my Visual Studio but hopefully you get the idea.