Test a consumer

In this example, a class is using the request client to check the status of an order.

Create the message contracts

using System;

public record CreateOrder(Guid OrderId);

public record OrderCreated(Guid OrderId);

Create the consumer

A consumer in the application that handles the CreateOrder message.

using System;
using System.Threading;
using System.Threading.Tasks;
using MassTransit;

public class CreateOrderConsumer :
    IConsumer<CreateOrder>
{
    public async Task Consume(ConsumeContext<CreateOrder> context)
    {
        await context.Publish(new OrderCreated(context.Message.OrderId));
    }
}

Create the test

To test a Request using the MassTransit Test Harness:

./tests/MyProject.Tests/CreateOrderConsumerTests.cs

namespace MyProject.Tests;

using System.Threading.Tasks;
using NUnit.Framework;
using MassTransit;
using MassTransit.Testing;

public class CreateOrderConsumerTests
{
    [Test]
    public async Task Should_create_an_order_and_produce_an_event()
    {
        await using var provider = new ServiceCollection()
            .AddMassTransitTestHarness(cfg =>
            {
                cfg.AddConsumer<CreateOrderConsumer>();
            })
            .BuildServiceProvider(true);

        var harness = await provider.StartTestHarness();

        var orderId = NewId.NextGuid();

        await harness.Bus.Publish(new CreateOrder(orderId));

        Assert.That(await harness.Consumed.Any<CreateOrder>(x => x.Message.OrderId == orderId));

        Assert.That(await harness.Published.Any<OrderCreated>(x => x.Message.OrderId == orderId));
    }
}