MassTransit–How to test consumers with dependencies

I’m using Dependency Injection in my MassTransit consumers. To test these consumers you can use MassTransit in-memory test harness;

	namespace UsingInMemoryTestHarness
	{
	using System.Threading.Tasks;
	using MassTransit;
	using MassTransit.Testing;
	using NUnit.Framework;
	[TestFixture]
	public class Using_the_test_harness
	{
	[Test]
	public async Task Should_be_easy()
	{
	var harness = new InMemoryTestHarness();
	var consumerHarness = harness.Consumer<SubmitOrderConsumer>();
	await harness.Start();
	try
	{
	}
	finally
	{
	await harness.Stop();
	}
	}
	}
	}

view raw MassTransitTestHarness.cs hosted with ❤ by GitHub

But when you try to use the code above with a consumer that has dependencies injected through the constructor, it will not work and you end up with the following error message:

'SubmitOrderConsumer' must be a non-abstract type with a public parameterless constructor in order to use it as parameter 'T' in the generic type or method 'ConsumerTestHarnessExtensions.Consumer<T>(BusTestHarness, string)'

To fix this, you have to change your test code and use the consumer factory method:

	namespace UsingInMemoryTestHarness
	{
	using System.Threading.Tasks;
	using MassTransit;
	using MassTransit.Testing;
	using NUnit.Framework;
	[TestFixture]
	public class Using_the_test_harness
	{
	[Test]
	public async Task Should_be_easy()
	{
	var harness = new InMemoryTestHarness();
	var services = new ServiceCollection();
	//TODO: add all dependencies
	var serviceProvider = services.BuildServiceProvider();
	var consumerHarness= harness.Consumer<SubmitOrderConsumer>(() =>
	{
	var consumer = serviceProvider.GetRequiredService<SubmitOrderConsumer>();
	return consumer;
	});
	await harness.Start();
	try
	{
	}
	finally
	{
	await harness.Stop();
	}
	}
	}
	}

view raw ConsumerFactory.cs hosted with ❤ by GitHub