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Mirror of gRPC calls

I want to be able to mirror all gRPC calls for some services to another set of services with same interface, in C#.
I think about writing extension method for GrpcClientFactory.CreateClient, to return class which would do two calls in parallel. Result from mirror is not needed, so I would return result from first call.
Is it best aproach for the task, or it is possible to make it better?

Pretty much what you described, in your case you can make use of IHttpClientFactory for creating http clients
public class GrpResponse
{
public string client { get; set; }
public HttpResponseMessage response { get; set; }
}
private async void ExecuteGrpRequest()
{
var payLoad = new HttpRequestMessage();
var grpTasks = new List<Task<GrpResponse>>
{
SendAsyc("real", payLoad),
SendAsyc("mock", payLoad)
};
var responses = await Task.WhenAll(grpTasks);
}
private async Task<GrpResponse> SendAsyc(string client, HttpRequestMessage message )
{
// IHttpClientFactory is _httpClientFacotry; injected from ctor
var httpClient = _httpClientFacotry.CreateClient(client);
return new GrpResponse
{
client = client,
response = await httpClient.SendAsync(new HttpRequestMessage())
};
}

Mocking a HttpClient handler when injected by IHttpClientFactory

I've created a custom library which automatically sets up Polly policies for specific services which depend on HttpClient.
This is done using the IServiceCollection extension methods and the typed client approach. A simplified example:
public static IHttpClientBuilder SetUpFooServiceHttpClient(this IServiceCollection services)
{
return services
.AddHttpClient<FooService>()
.AddPolicyHandler(GetRetryPolicy());
}
public class FooService
{
private readonly HttpClient _client;
public FooService(HttpClient httpClient)
{
_client = httpClient;
}
public void DoJob()
{
var test = _client.GetAsync("http://example.com");
}
}
Note that my real code uses a generic type and an options builder, but I've omitted that part to keep it simple. The purpose of my tests is to confirm that my options builder correctly applies the policies that I want it to apply. For the sake of example here, let's just assume that it's a hardcoded retry policy which I want to test.
I now want to test if this library correctly registers the Polly policies to my injected HttpClient dependencies.
Note
There are many answers to be found online and on StackOverflow where the suggestion is to construct the HttpClient yourself, i.e.: new HttpClient(new MyMockedHandler());, but this defeats my purpose of needing to test if the actual IHttpClientFactory is constructing httpclients with the requested policies.
To that end, I want to test with a real HttpClient which was generated by a real IHttpClientFactory, but I want its handler to be mocked so I can avoid making actual web requests and artificially cause bad responses.
I'm using AddHttpMessageHandler() to inject a mocked handler, but the factory seems to be ignoring that.
Here's my test fixture:
public class BrokenDelegatingHandler : DelegatingHandler
{
public int SendAsyncCount = 0;
protected override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request,
CancellationToken cancellationToken)
{
SendAsyncCount++;
return Task.FromResult(new HttpResponseMessage(HttpStatusCode.InternalServerError));
}
}
private BrokenDelegatingHandler _brokenHandler = new BrokenDelegatingHandler();
private FooService GetService()
{
var services = new ServiceCollection();
services.AddTransient<BrokenDelegatingHandler>();
var httpClientBuilder = services.SetUpFooServiceHttpClient();
httpClientBuilder.AddHttpMessageHandler(() => _brokenHandler);
services.AddSingleton<FooService>();
return services
.BuildServiceProvider()
.GetRequiredService<FooService>();
}
And here's my test:
[Fact]
public void Retries_client_connection()
{
int retryCount = 3;
var service = GetService();
_brokenHandler.SendAsyncCount.Should().Be(0); // PASS
var result = service.DoJob();
_brokenHandler.SendAsyncCount.Should().Be(retryCount); // FAIL: expected 3 but got 0
}
When I debug the test, the handler's breakpoint is never hit, and the response comes back as a 200 (because it actually connected to the URL, instead of hitting the mocked handler).
Why is my mocked handler being ignored by the http client factory?
Note that I will also accept any answer that allows me to test the policies in another valid way.
I'm aware I can just use a broken URL string but I'm going to need to test specific http responses in my tests.

We had a similar problem few months ago. How to test that the injected HttpClient is decorated with the correct Policies. (We have used a Retry > CircuitBreaker > Timeout policy chain).
We ended up to create several integration tests. We have used WireMock.NET to create a server stub. So, the whole point of this was to let the ASP.NET DI do its magic and then scrutinize the stub's logs.
We have created two base classes which wrapped the WireMock setup (we had a POST endpoint).
FlawlessServer
internal abstract class FlawlessServiceMockBase
{
protected readonly WireMockServer server;
private readonly string route;
protected FlawlessServiceMockBase(WireMockServer server, string route)
{
this.server = server;
this.route = route;
}
public virtual void SetupMockForSuccessResponse(IResponseBuilder expectedResponse = null,
HttpStatusCode expectedStatusCode = HttpStatusCode.OK)
{
server.Reset();
var endpointSetup = Request.Create().WithPath(route).UsingPost();
var responseSetup = expectedResponse ?? Response.Create().WithStatusCode(expectedStatusCode);
server.Given(endpointSetup).RespondWith(responseSetup);
}
}
FaultyServer
(We have used scenarios to simulate timeouts)
internal abstract class FaultyServiceMockBase
{
protected readonly WireMockServer server;
protected readonly IRequestBuilder endpointSetup;
protected readonly string scenario;
protected FaultyServiceMockBase(WireMockServer server, string route)
{
this.server = server;
this.endpointSetup = Request.Create().WithPath(route).UsingPost();
this.scenario = $"polly-setup-test_{this.GetType().Name}";
}
public virtual void SetupMockForFailedResponse(IResponseBuilder expectedResponse = null,
HttpStatusCode expectedStatusCode = HttpStatusCode.InternalServerError)
{
server.Reset();
var responseSetup = expectedResponse ?? Response.Create().WithStatusCode(expectedStatusCode);
server.Given(endpointSetup).RespondWith(responseSetup);
}
public virtual void SetupMockForSlowResponse(ResilienceSettings settings, string expectedResponse = null)
{
server.Reset();
int higherDelayThanTimeout = settings.HttpRequestTimeoutInMilliseconds + 500;
server
.Given(endpointSetup)
.InScenario(scenario)
//NOTE: There is no WhenStateIs
.WillSetStateTo(1)
.WithTitle(Common.Constants.Stages.Begin)
.RespondWith(DelayResponse(higherDelayThanTimeout, expectedResponse));
for (var i = 1; i < settings.HttpRequestRetryCount; i++)
{
server
.Given(endpointSetup)
.InScenario(scenario)
.WhenStateIs(i)
.WillSetStateTo(i + 1)
.WithTitle($"{Common.Constants.Stages.RetryAttempt} #{i}")
.RespondWith(DelayResponse(higherDelayThanTimeout, expectedResponse));
}
server
.Given(endpointSetup)
.InScenario(scenario)
.WhenStateIs(settings.HttpRequestRetryCount)
//NOTE: There is no WillSetStateTo
.WithTitle(Common.Constants.Stages.End)
.RespondWith(DelayResponse(1, expectedResponse));
}
private static IResponseBuilder DelayResponse(int delay) => Response.Create()
.WithDelay(delay)
.WithStatusCode(200);
private static IResponseBuilder DelayResponse(int delay, string response) =>
response == null
? DelayResponse(delay)
: DelayResponse(delay).WithBody(response);
}
Simple test for Slow processing
(proxyApiInitializer is a instance of a WebApplicationFactory<Startup> derived class)
[Fact]
public async Task GivenAValidInout_AndAServiceWithSlowProcessing_WhenICallXYZ_ThenItCallsTheServiceSeveralTimes_AndFinallySucceed()
{
//Arrange - Proxy request
HttpClient proxyApiClient = proxyApiInitializer.CreateClient();
var input = new ValidInput();
//Arrange - Service
var xyzSvc = new FaultyXYZServiceMock(xyzServer.Value);
xyzSvc.SetupMockForSlowResponse(resilienceSettings);
//Act
var actualResult = await CallXYZAsync(proxyApiClient, input);
//Assert - Response
const HttpStatusCode expectedStatusCode = HttpStatusCode.OK;
actualResult.StatusCode.ShouldBe(expectedStatusCode);
//Assert - Resilience Policy
var logsEntries = xyzServer.Value.FindLogEntries(
Request.Create().WithPath(Common.Constants.Routes.XYZService).UsingPost());
logsEntries.Last().MappingTitle.ShouldBe(Common.Constants.Stages.End);
}
XYZ Server init:
private static Lazy<WireMockServer> xyzServer;
public ctor()
{
xyzServer = xyzServer ?? InitMockServer(API.Constants.EndpointConstants.XYZServiceApi);
}
private Lazy<WireMockServer> InitMockServer(string lookupKey)
{
string baseUrl = proxyApiInitializer.Configuration.GetValue<string>(lookupKey);
return new Lazy<WireMockServer>(
WireMockServer.Start(new FluentMockServerSettings { Urls = new[] { baseUrl } }));
}
I hope this can help you.

How do I test the integration between the Global error handling middleware and my controller in ASP.Net Core?

I'm trying to write some test with XUnit, specifically I'd like to have a test that ensures that when a certain exception is thrown it gets remapped into a meaningful error code.
I already set up the Global error handling middleware and it works correctly.
Here there is some example code of how my solution works:
My controller with a post endpoint that can return 200 or 404
//Controller
[HttpPost]
[ProducesResponseType(200)]
[ProducesResponseType(404)]
public async Task<StatusCodeResult> Create([FromBody] Request request) {
//Process request
handler.Handle(request);
return Ok();
}
The Middleware for the Global error handling that remaps exceptions into Error codes
//StartUp Middleware
app.UseExceptionHandler(builder => {
builder.Run(handler: async context => {
IExceptionHandlerFeature error = context.Features.Get<IExceptionHandlerFeature>();
if (error != null) {
int statusCode = (int)GetStatusCodeForException(error.Error);
context.Response.StatusCode = statusCode;
context.Response.ContentType = "application/json";
await context.Response.WriteAsync(new ErrorDetails { StatusCode = statusCode, Message = error.Error.Message }.ToString());
}
});
});
And then my test in where I arrange some mocks, instantiate the controller and call the Create method
//UnitTest
[Fact]
public async Task Test()
{
//Arrange
var mockHandler = new Mock<IHandler>();
mockHandler.Setup(handler => handler.Handle(It.IsAny<Request>())).Throws(new CustomException(It.IsAny<string>()));
MyController myController = new MyController();
//Act
var statusCodeResult = await myController.Create(request);
//Assert
StatusCodeResult result = Assert.IsType<NotFoundResult>(statusCodeResult);
}
Here I want to ensure that the CustomException is remapped into a 404 status code. How do I do it? Any help is appreciated.

In your test the middleware is not available. You need to spin up a hosting environment to do that, the package Microsoft.AspNetCore.TestHost provides you with one that you can use for testing:
[Fact]
public async Task Test1()
{
using var host = new TestServer(Program.CreateHostBuilder(null));
var client = host.CreateClient();
var requestMessage = new HttpRequestMessage(HttpMethod.Get, "/api/controller");
var result = await client.SendAsync(requestMessage);
var status = result.StatusCode;
// TODO: assertions
}
Now when you call your API in a way an exception is thrown, the middleware should be executed and covered.

You can use the WebApplicationFactory class from the Microsoft.AspNetCore.Mvc.Testing nuget package. This bootstraps your application in-memory to allow for end to end functional tests. Rather than calling individual action methods you can make calls via HttpClient to ensure all middleware etc is called.
You use the Startup class that you have already defined in your main entry project and can add mock/fake objects to the IoC container as required. This allows you to verify/setup any dependencies.
You can then inject this as an IClassFixture. Once injected calling .CreateClient() on the instance will return an HttpClient, through which you can make requests.
Here is an example implementation:
// app factory instance
public class TestAppFactory : WebApplicationFactory<Startup>
{
// mock for setup/verify
public Mock<IHandler> MockHandler { get; } = new Mock<IHandler>();
protected override void ConfigureWebHost(IWebHostBuilder builder)
{
builder.ConfigureTestServices(services =>
{
services.AddSingleton(MockHandler);
});
}
}
public class MyTestClass : IClassFixture<TestAppFactory>
{
private readonly TestAppFactory _factory;
private readonly HttpClient _client;
private readonly Mock<IHandler> _mockHandler;
public MyTestClass(TestAppFactory factory)
{
_factory = factory;
_client = factory.CreateClient();
_mockHandler = factory.MockHandler;
}
[Fact]
public async Task Test()
{
// make calls via _client
}
}

XUnit mocking a method but doesn't return expected result

I am using moq in XUnit test but for some reason the mock is not working properly. Here's my unit test:
[Fact]
public async Task SampleUnitTest()
{
//Arrange
var httpClient = new HttpClient(new FakeHttpMessageHandler());
_mockConstructRequest.Setup(x => x.ConstructRequestString(searchRequestModel))
.Returns("a sample string");
var service = new LibraryService(_mockConstructRequest.Object);
//Act
var response = service.GetResponse(new Request(), httpClient);
//Assert
response.Should().BeNull();
}
private class FakeHttpMessageHandler : HttpMessageHandler
{
public Func<HttpRequestMessage, CancellationToken, HttpResponseMessage> HttpRequestHandler { get; set; } =
(r, c) =>
new HttpResponseMessage
{
ReasonPhrase = r.RequestUri.AbsoluteUri,
StatusCode = HttpStatusCode.OK
};
protected override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
{
return Task.FromResult(HttpRequestHandler(request, cancellationToken));
}
}
And here is the actual code and I am trying to test GetResponse method.
public class LibraryService : ILibraryService
{
private IConfiguration _configuration;
private IRequestConstructor _requestContructor;
public LibraryService (IRequestConstructor requestConstructor)
{
_requestConstructor = requestConstructor;
}
public async Task<Response> GetResponse(Request request, HttpClient client)
{
//construct request
string requestString = _constructRequestString.ConstructRequestString(request, client);
return null;
}
}
public class RequestContructor : IRequestContructor
{
public string ConstructRequestString(Request request)
{
return "a request string";
}
}
I was trying to step through the code from my unit test but when the break point is at this line, requestString variable is null while it is supposed to return "a sample string". Anyone knows why?
string requestString = _constructRequestString.ConstructRequestString(request, client);

As far as I can see you are mocking incorrectly:
Your mock:
_mockConstructRequest.Setup(x => x.ConstructRequestString(searchRequestModel))
.Returns("a sample string");
Method you are calling:
_constructRequestString.ConstructRequestString(request, client);
Should not it be something like this:
_mockConstructRequest.Setup(x => x.ConstructRequestString(It.IsAny<Request>(),It.IsAny<HttpClient>()))
.Returns("a sample string");
On top of that:
Try to initialize your mocks and your "classUnderTest" in constructor instead of in each test, it will run each time before the test and will do everything for you. For example:
public class UnitTestClass{
private readonly ClassUnderTest _classUnderTest;
private readonly Mock<ClassUnderTestDependecy> mockedInstance;
public UnitTestClass {
mockedInstance= new Mock<ClassUnderTestDependecy>();
_classUnderTest= new ClassUnderTest (ClassUnderTestDependecy.Object);
}
}

ASP.NET MVC WebAPI create ViewModel from async tasks

I write web application using ASP.NET MVC WebAPI and I want to transform current synchronous code to asynchronous for optimization. Problem is that I fill ViewModel with multiple objects taken from repository. These calls from repository should be async.
Let's asume I have signature for repository calls respecting this interface
public interface ICompanyRepository
{
IEnumerable<Company> GetCompanies();
IEnumerable<Address> GetAddresses();
}
ViewModels definition
public class CompaniesFullViewModel
{
public IEnumerable<Company> Companies { get; set; }
public IEnumerable<Address> Addresses { get; set; }
}
And controller:
public class CompanyController
{
public readonly ICompanyRepository Repository { get; private set; }
public CompanyController(IRepository repository)
{
Repository = repository;
}
[ResponseType(typeof(CompaniesFullViewModel))]
public HttpResponseMessage Get()
{
var companies = Repository.GetCompanies();
var addresses = Repository.GetAddresses();
HttpStatusCode statusCode = companies.Any()
? HttpStatusCode.OK
: HttpStatusCode.PartialContent;
return
Request.CreateResponse(
statusCode,
new CompaniesFullViewModel
{
Companies = companies,
Addresses = addresses
});
}
}
Furthermore I have tests implemented to the controller:
[TestClass]
public sealed class CompanyTestController : BaseTestController
{
#region Fields
private static Mock<ICompanyRepository> _repositoryMock;
private static CompanyController _controller;
#endregion
[ClassInitialize]
public static void Initialize(TestContext testContext)
{
// Mock repository
_repositoryMock = new Mock<ICompanyRepository>();
DependencyResolver.Default.Container.RegisterInstance(_repositoryMock.Object);
// Create controller
_controller =
DependencyResolver.Default.Container.Resolve<CompanyController>();
// Init request
_controller.Request = new HttpRequestMessage();
_controller.Request.SetConfiguration(new HttpConfiguration());
}
[ClassCleanup]
public static void Cleanup()
{
_controller.Dispose();
}
[TestMethod]
public void Get_ActionExecutes_ReturnsEmptyCompaniesViewModel()
{
var companies = new List<Company>();
var addresses = new List<Address>();
// Setup fake method
_repositoryMock
.Setup(c => c.GetCompanies())
.Returns(companies);
_repositoryMock
.Setup(c => c.GetAddresses())
.Returns(addresses);
// Execute action
var response = _controller.Get();
// Check the response
Assert.AreEqual(HttpStatusCode.PartialContent, response.StatusCode);
}
}
How can I convert the controller to async, if the repository is async and the signature looks like this:
public interface ICompanyRepository
{
Task<IEnumerable<Company>> GetCompaniesAsync();
Task<IEnumerable<Address>> GetAddressesAsync();
}

What you need to do is change the Controller action to be async as well, and change the return type to Task<>. You can then await your asynchronous repository calls:
[ResponseType(typeof(CompaniesFullViewModel))]
public async Task<HttpResponseMessage> Get() // async keyword.
{
var companies = await Repository.GetCompaniesAsync(); // await
var addresses = await Repository.GetAddressesAsync(); // await
HttpStatusCode statusCode = companies.Any()
? HttpStatusCode.OK
: HttpStatusCode.PartialContent;
return
Request.CreateResponse(
statusCode,
new CompaniesFullViewModel
{
Companies = companies,
Addresses = addresses
});
}
By convention, you can also change the name of the controller action to end in Async as well, although if you are using RESTful conventions and / or Routing attributes, the actual name of the controller action isn't really important.
Testing
I use XUnit and NUnit, but it seems MSTest also supports testing of asynchronous methods, and Moq also provides Async versions of the setups:
[Test]
public async Task Get_ActionExecutes_ReturnsEmptyCompaniesViewModel() // async Task
{
var companies = new List<Company>();
var addresses = new List<Address>();
// Setup fake method
_repositoryMock
.Setup(c => c.GetCompaniesAsync())
.ReturnsAsync(companies); // Async
_repositoryMock
.Setup(c => c.GetAddressesAsync())
.ReturnsAsync(addresses); // Async
// Execute action
var response = await _controller.Get(); // Await
// Check the response
Assert.AreEqual(HttpStatusCode.PartialContent, response.StatusCode);
_repositoryMock.Verify(m => m.GetAddressesAsync(), Times.Once);
_repositoryMock.Verify(m => m.GetCompaniesAsync(), Times.Once);
}
As an aside, it seems you are using Setter Dependency injection. An alternative is to use Constructor injection, which has the benefit of ensuring that the class is always in a valid state (i.e. there is no transient state while it is waiting for the dependencies to be set). This also allows the dependencies (your repository in this case) to be made readonly.