使用外部事件对 C# Azure 耐用 Function 进行单元测试

Question

I've got an Azure Durable Function orchestrator that waits for two external events. Once they've both been received, the orchestrator calls an activity function.

Is there a way to unit test this orchestrator, to verify that the activity function is called only after both events have been received?

Here's the orchestrator function code:

[FunctionName("MyOrchestrator")]

public static async Task MyOrchestrator(

    [OrchestrationTrigger] IDurableOrchestrationContext context)

{
    var event1 = context.WaitForExternalEvent<string>("Event1");
    var event2 = context.WaitForExternalEvent<string>("Event2");
    await Task.WhenAll(event1, event2);

    await context.CallActivityAsync<object>("Activity1", null);
    context.SetOutput(new { Status = "Complete" });
}

Answer 1

If the mocked context is arranged properly then the activity can only happen after awaiting the two external event tasks to complete.

//Arrange
var context = new Mock<IDurableOrchestrationContext>(); //MOQ

context.Setup(_ => _.WaitForExternalEvent<string>(It.IsAny<string>()))
    .Returns(async () => {
        await Task.Delay(10); //Delay is optional
        return "";
    });

context.Setup(_ => _.CallActivityAsync<object>(It.IsAny<string>(), It.IsAny<object>()))
    .ReturnsAsync(null);

//Act
await MyFunction.MyOrchestrator(context.Object);

//Assert
context.Verify(_ => _.WaitForExternalEvent<string>("Event1"));
context.Verify(_ => _.WaitForExternalEvent<string>("Event2"));
context.Verify(_ => _.CallActivityAsync<object>("Activity1", null));
context.Verify(_ => _.SetOutput(It.IsAny<object>()));

In the above example, using MOQ, the events are setup generically to delay before completing the task. Only then would the activity be invoked.

The test then verifies specific invocations to assert the expected behaviors.

As for how useful this unit test is, not very much, since it is basically testing that framework code awaits as expected.