1. Introduction
From time to time it might happen, that you need to test certain parts of your ASP.NET Core configuration without hitting publicly visible business-related controllers. For instance, in my case, I wanted to make sure that my ASP.NET Core API behavior is consistent with the original API written in Nancy. As you might expect there are quite a lot of differences between both of the frameworks, so let’s focus on testing one thing, namely non-nullable reference type handling. Long story short, in order to have the same behavior in ASP.NET Core as in Nancy I had to add the following line of configuration
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// This method gets called by the runtime. Use this method to add services to the container. public void ConfigureServices(IServiceCollection services) { services.AddControllers(opts => opts.SuppressImplicitRequiredAttributeForNonNullableReferenceTypes = true) .AddNewtonsoftJson(); } |
This one prevents ASP.NET Core from marking non-nullable reference type properties in request as required. Having that configuration ready, I wanted to test it with an end to end test. Because there was no business-related logic yet, I needed to figure out the way of adding API controllers to my application directly from the integration tests. Here is how you can achieve that.
2. Accessing ApplicationPartManager from integration tests
ASP.NET Core is able to compose your API from different parts thanks to ApplicationPartManager. By default, you don’t use it directly but rather with IMvcBuilder AddApplicationPart extension method while setting up your application
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// This method gets called by the runtime. Use this method to add services to the container. public void ConfigureServices(IServiceCollection services) { services.AddControllers() .AddApplicationPart(typeof(SomeClass).Assembly) .AddNewtonsoftJson(); } |
However, there is no easy way of getting IMvcBuidler from the integration tests(at least I didn’t find a proper way of doing that without tampering too much with the original application pipeline) so we need to access ApplicationPartManager directly. Inspecting the source code of the framework you will find that ApplicationPartManager can be retrieved directly from IServiceCollection with following code
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private static ApplicationPartManager GetApplicationPartManager(IServiceCollection services) { var manager = GetServiceFromCollection<ApplicationPartManager>(services); if (manager == null) { manager = new ApplicationPartManager(); var environment = GetServiceFromCollection<IWebHostEnvironment>(services); var entryAssemblyName = environment?.ApplicationName; if (string.IsNullOrEmpty(entryAssemblyName)) { return manager; } manager.PopulateDefaultParts(entryAssemblyName); } return manager; } private static T GetServiceFromCollection<T>(IServiceCollection services) { return (T)services .LastOrDefault(d => d.ServiceType == typeof(T)) ?.ImplementationInstance; } |
Applying similar code to the WebApplicationFactory will allow us to add controllers directly from tests
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[Fact] public async Task DoesNotReturnBadRequest_WhenNonNullableTypeHasNoValue_FirstAttempt() { var webApplicationFactory = new WebApplicationFactory<Startup>() .WithWebHostBuilder( builder => builder.ConfigureServices(services => { var partManager = (ApplicationPartManager) services .Last(descriptor => descriptor.ServiceType == typeof(ApplicationPartManager)) .ImplementationInstance; partManager.ApplicationParts.Add(new AssemblyPart(GetType().Assembly)); })); var expectedResponse = new Request { Id = "1" }; var httpClient = webApplicationFactory.CreateClient(); var httpResponseMessage = await httpClient.GetAsync("test?id=1"); httpResponseMessage.IsSuccessStatusCode.Should().BeTrue(); var rawContent = await httpResponseMessage.Content.ReadAsStringAsync(); var result = JsonConvert.DeserializeObject<Request>(rawContent); result.Should().BeEquivalentTo(expectedResponse); } [ApiController] public class MvcOptionsTestController : ControllerBase { [HttpGet("test")] public object Get([FromQuery] Request request) { return request; } } public class Request { public string Id { get; set; } public string OtherId { get; set; } } |
3. Handling private controllers
The solution presented below works nice, however it has couple of drawbacks. First of all, it only discovers public non-nested controllers. Second of all, it will always add all controllers from given assembly – which potentially might affect other integration tests. In order to get rid of these drawbacks, we need to tell ApplicationPartManager to include only selected controllers. We can achieve that by adding additional IApplicationFeatureProvider<ControllerFeature> to the list of FeatureProviders.
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public class ExternalControllersFeatureProvider : IApplicationFeatureProvider<ControllerFeature> { private readonly Type[] _controllers; public ExternalControllersFeatureProvider(params Type[] controllers) { _controllers = controllers ?? Array.Empty<Type>(); } public void PopulateFeature(IEnumerable<ApplicationPart> parts, ControllerFeature feature) { foreach (var controller in _controllers) { feature.Controllers.Add(controller.GetTypeInfo()); } } } [Fact] public async Task DoesNotReturnBadRequest_WhenNonNullableTypeHasNoValue() { var webApplicationFactory = new WebApplicationFactory<Startup>() .WithWebHostBuilder( builder => builder.ConfigureServices(services => { var partManager = (ApplicationPartManager) services .Last(descriptor => descriptor.ServiceType == typeof(ApplicationPartManager)) .ImplementationInstance; partManager.FeatureProviders.Add(new ExternalControllersFeatureProvider(typeof(MvcOptionsTestController))); })); // rest of the code omitted for brevity } |
Putting it all together and applying some refactoring we will end up with following code
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internal static class WebHostBuilderExtensions { public static IWebHostBuilder WithAdditionalControllers(this IWebHostBuilder builder, params Type[] controllers) { return builder.ConfigureTestServices( services => { var partManager = GetApplicationPartManager(services); partManager.FeatureProviders.Add(new ExternalControllersFeatureProvider(controllers)); }); } private static ApplicationPartManager GetApplicationPartManager(IServiceCollection services) { var partManager = (ApplicationPartManager)services .Last(descriptor => descriptor.ServiceType == typeof(ApplicationPartManager)) .ImplementationInstance; return partManager; } private class ExternalControllersFeatureProvider : IApplicationFeatureProvider<ControllerFeature> { private readonly Type[] _controllers; public ExternalControllersFeatureProvider(params Type[] controllers) { _controllers = controllers ?? Array.Empty<Type>(); } public void PopulateFeature(IEnumerable<ApplicationPart> parts, ControllerFeature feature) { foreach (var controller in _controllers) { feature.Controllers.Add(controller.GetTypeInfo()); } } } } public class MvcOptionsConfigurationTests { [Fact] public async Task DoesNotReturnBadRequest_WhenNonNullableTypeHasNoValue() { var webApplicationFactory = new WebApplicationFactory<Startup>() .WithWebHostBuilder( builder => builder.WithAdditionalControllers(typeof(MvcOptionsTestController))); var httpClient = webApplicationFactory.CreateClient(); var expectedResponse = new Request { Id = "1" }; var httpResponseMessage = await httpClient.GetAsync("test?id=1"); httpResponseMessage.IsSuccessStatusCode.Should().BeTrue(); var rawContent = await httpResponseMessage.Content.ReadAsStringAsync(); var result = JsonConvert.DeserializeObject<Request>(rawContent); result.Should().BeEquivalentTo(expectedResponse); } [ApiController] private class MvcOptionsTestController: ControllerBase { [HttpGet("test")] public object Get([FromQuery] Request request) { return request; } } private class Request { public string Id { get; set; } public string OtherId { get; set; } } } |
Source code for this post can be found here