Mocking MediatR 3 with Moq

Question

We\'ve recently started using MediatR to allow us to de-clutter controller actions as we re-factor a large customer facing portal and convert it all to C#. As part of this we ar

Answer 1

You need to handle the await of the async operation of the Send methods as they return tasks.

/// 

/// Asynchronously send a request to a single handler
/// 
/// Response type
/// Request object
/// Optional cancellation token
/// A task that represents the send operation. The task result contains the handler response
Task Send(IRequest request, CancellationToken cancellationToken = default(CancellationToken));

/// 

/// Asynchronously send a request to a single handler without expecting a response
/// 
/// Request object
/// Optional cancellation token
/// A task that represents the send operation.
Task Send(IRequest request, CancellationToken cancellationToken = default(CancellationToken));

That means you need to have the mock return a task to allow the async process to continue the flow

mediator
    .Setup(m => m.Send(It.IsAny(), It.IsAny()))
    .ReturnsAsync(new Notification()) //<-- return Task to allow await to continue
    .Verifiable("Notification was not sent.");

//...other code removed for brevity

mediator.Verify(x => x.Send(It.IsAny(), It.IsAny()), Times.Once());