Writing unit tests for orchestration functions in Azure Durable Functions - moq

Question

I'm trying to learn how to write unit tests for durable function. Here is my code:
[FunctionName("OrchestratorFunction")]
public async Task RunOrchestrator([OrchestrationTrigger] IDurableOrchestrationContext context)
{
var jobs = await context.CallActivityAsync<List<Job>>("JobsReaderFunction"), null);
if (jobs != null && jobs .Count > 0)
{
var processingTasks = new List<Task>();
foreach (var job in jobs)
{
Task processTask = context.CallSubOrchestratorAsync("SubOrchestratorFunction"), job);
processingTasks.Add(processTask);
}
await Task.WhenAll(processingTasks);
}
}
[FunctionName("SubOrchestratorFunction")]
public async Task RunSubOrchestrator([OrchestrationTrigger] IDurableOrchestrationContext context)
{
var job = context.GetInput<Job>();
var group = await context.CallActivityAsync<Group>("GroupReaderFunction"), job);
await context.CallActivityAsync("EmailSenderFunction", group);
var canWriteToGroup = await context.CallActivityAsync<bool>("GroupVerifierFunction", job);
await context.CallActivityAsync("JobStatusUpdaterFunction", new JopStatusUpdaterRequest { CanWriteToGroup = canWriteToGroup, Job = job });
await context.CallActivityAsync("TopicMessageSenderFunction", job);
}
How do I write a test that covers Orchestrator, SubOrchestrator and Activity functions? Please let me know.
Here is my test so far:
[TestMethod]
public async Task VerifyOrchestrator()
{
var jobs = <code to get jobs>
var context = new Mock<IDurableOrchestrationContext>();
context.Setup(m => m.CallActivityAsync<List<Job>>("JobsReaderFunction", It.IsAny<object>())).ReturnsAsync(jobs);
await _orchestratorFunction.RunOrchestrator(context.Object);
}
UPDATE:
I updated the test method to:
[TestMethod]
public async Task VerifyJobs()
{
var jobs = <code to get jobs>
var context = new Mock<IDurableOrchestrationContext>();
context.Setup(x => x.CallSubOrchestratorAsync("SubOrchestratorFunction"), It.IsAny<object>())).Returns(() => _orchestratorFunction.RunSubOrchestrator(context.Object));
await _orchestratorFunction.RunOrchestrator(context.Object);
}
which gives me an error:
context.Setup(x => x.CallSubOrchestratorAsync("SubOrchestratorFunction", It.IsAny<object>())).Returns(async () => await It.IsAny<Task>());
await _orchestratorFunction.RunOrchestrator(context.Object);
context.Verify(m => m.CallSubOrchestratorAsync("SubOrchestratorFunction", It.IsAny<string>(), It.IsAny<object>()),Times.Once);
The above gives a null exception.

Answer 1

The context is mocked acording to the line:
var context = new Mock<IDurableOrchestrationContext>();
This means that when you execute Context.CallSubOrchestratorAsync("SubOrchestratorFunction") moq search for setup for the method.
Because the method doesn't have any setup, it runs nothing and returns the default return value.
If you want to execute RunSubOrchestrator, you should setup it:
context.Setup(x => x.CallSubOrchestratorAsync("SubOrchestratorFunction", It.IsAny<object>())).Returns(() => _orchestratorFunction.RunSubOrchestrator(context.Object))