如何使用 WebApplicationFactory 在 TestServer 中切换服务？

Question

I'm using custom WebApplication factory

public class CustomWebApplicationFactory<TStartup> : WebApplicationFactory<TStartup> where TStartup: class {
    protected override void ConfigureWebHost(IWebHostBuilder builder) {
        builder.ConfigureServices(services => {
            // Create a new service provider.
            var serviceProvider = new ServiceCollection()
                .AddEntityFrameworkInMemoryDatabase()
                .BuildServiceProvider();

            services.AddDbContext<GrabGoContext>(options => {
                options.UseInMemoryDatabase("GrabGoDb");
                options.UseInternalServiceProvider(serviceProvider);
            });

            services.AddSingleton<TestEmailServer>();
            services.AddScoped<IEmailProvider, TestEmailProvider>(); // <- HERE
        });
        base.ConfigureWebHost(builder);
    }

I want to switch my default IEmailProvider service called DefaultEmailProvider to my special TestEmailProvider , but the problem is that the method ConfigureWebHost is executed before Startup.ConfigureServices(IServiceCollection services) , so my service DefaultEmailProvider is set after TestEmailProvider . Therefore in my ClientController service DeafultEmailProvider is used instead of test service.

My question is:

How can I switch service DefaultEmailProvider with my TestEmailProvider using WebApplicationFactory?

@Update

Ok, I've managed to go deeper. I found that method builder.ConfigureTestServices() overrides other services. But when switch this in my ConfigureWebHost(IWebHostBuilder builder) method and I try to create new HttpClient using CreateClient() it throws:

System.InvalidOperationException: 'A ConfigureServices method that returns an IServiceProvider is not compatible with the use of one or more IStartupConfigureServicesFilter. Use a void returning ConfigureServices method instead or a ConfigureContainer method.'

@Update 28.05.2019

Still looking for better solution , but I've manage to do sort of hack .

In my Startup.cs I've swapped my

services.AddScoped<IEmailProvider, SendGridEmailProvider>();

with TryAdd[Something]

services.TryAddScoped<IEmailProvider, SendGridEmailProvider>();

Answer 1

You should be able to do it in the ConfigureWebHost similar to the below:

public class CustomWebApplicationFactory : WebApplicationFactory<Startup>
{
    protected override void ConfigureWebHost(IWebHostBuilder builder) 
    {
        builder.ConfigureServices(services => 
        {
            // Remove application IEmailProvider service
            var emailProviderDescriptor = services.SingleOrDefault(d => d.ServiceType == typeof(IEmailProvider));
            if (emailProviderDescriptor != null)
            {
                services.Remove(emailProviderDescriptor);
            }

            // Add new test service(s)
            services.AddScoped<IEmailProvider, TestEmailProvider>();
            services.AddSingleton<TestEmailServer>(); // May need to remove using the descriptor similar to IEmailProvider

            // Remove the app's GrabGoContext registration, add in memory one then seed data.
            var dbDescriptor = services.SingleOrDefault(d => d.ServiceType == typeof(DbContextOptions<GrabGoContext>));
            if (dbDescriptor != null)
            {
                services.Remove(dbDescriptor);
            }

            services.AddDbContext<GrabGoContext>(options =>
            {
                options.UseInMemoryDatabase("InMemoryDbForTesting");
            });

            var serviceProvider = services.BuildServiceProvider();
            using var scope = serviceProvider.CreateScope();
            var scopedServices = scope.ServiceProvider;
            var grabGoContext = scopedServices.GetRequiredService<GrabGoContext>();

            // Seed your db here & save..
            grabGoContext.SaveChanges();
        });

        base.ConfigureWebHost(builder);
    }
}

You may want to make it easier on yourself and just implement the factory, like the above, rather than keep it generic. I've also added slightly different code for your in-memory database.

It hasn't been compiled, but the syntax shouldn't be far off. Hope that helps.

Answer 2

You can do it based on Environment. This is just code to point you in the right direction.

  public IHostingEnvironment HostingEnvironment { get; }

    public void ConfigureServices(IServiceCollection services)
    {
        if (HostingEnvironment.IsDevelopment())
        {
            services.AddTransient<ITestService, TestService>();
        }
        else
        {
            services.AddTransient<IRealService, RealService>();
        }

        // other services
    }

I hope this helps.

Answer 3

I just spent several hours trying to do a similar thing (override the services in my integration tests). Turns out ConfigureServices runs before the SUT (subject under test) service configuration. ConfigureTestServices , however, runs after and is where you would override with your mocks.

The docs are not at all clear on this, though I did, after the fact, find this:

https://docs.microsoft.com/en-us/aspnet/core/test/integration-tests?view=aspnetcore-3.0#inject-mock-services

Answer 4

You can try this, call ConfigureTestServices rather than call ConfigureServices :

protected override void ConfigureWebHost(IWebHostBuilder builder)
    {
        builder
            .UseEnvironment("Test")
            .ConfigureTestServices(services =>
            {
                  // Put your logic here
            }); ;
    }