Retrieving ASP.NET Core 3.1 database context in Xunit integration test

Question

I've been creating integration tests using Xunit for a .NET Core 3.1 web app that uses a database. For testing I've swapped to an in-memory database following along from the Microsoft Documentation. The CustomWebApplicationFactory code is:

public class CustomWebApplicationFactory<TStartup> : WebApplicationFactory<TStartup> where TStartup : class
        {
        protected override void ConfigureWebHost(IWebHostBuilder webHostBuilder)
            {
            webHostBuilder.ConfigureServices(services =>
                {
                    // Remove the app's database  registration.
                    var serviceDescriptor = services
                                                .SingleOrDefault(d => d.ServiceType == typeof(DbContextOptions<MyDbContext>));

                    if (serviceDescriptor != null)
                        {
                        services.Remove(serviceDescriptor);
                        }

                    // Add MyDbContext using an in-memory database for testing.
                    services.AddDbContext<MyDbContext>(options =>
                    {
                        options.UseInMemoryDatabase("InMemoryDbForTesting");
                    });

                    var servicesProvider = services.BuildServiceProvider();

                    // Create a scope to obtain a reference to the database context (MyDbContext).
                    using (var serviceScope = servicesProvider.CreateScope())
                        {
                        var scopedServices = serviceScope.ServiceProvider;
                        var db = scopedServices.GetRequiredService<MyDbContext>();
                        var logger = scopedServices.GetRequiredService<ILogger<CustomWebApplicationFactory<TStartup>>>();

                        db.Database.EnsureCreated();                                                                                                                                         // Ensure the database is created.

                        try
                            {
                            DatabaseSeeding.voidInitialiseCazIdentityProviderDatabase(db);                                                                                                                              // Seed the database with test data.
                            }
                        catch (Exception ex)
                            {
                            logger.LogError(ex, $"An error occurred seeding the database with data. Error: {ex.Message}");
                            }
                        }
                });
            }

My basic page tests work fine with this arrangement, but I now want to check to see if the in-memory database has been corrected modified by the integration test. Whatever is happening, the reference to the database is not ending up in the Xunit DI container (if such a thing exists). My test class is initialised with the following code:

    public class IdpUserServiceTests : IClassFixture<CustomWebApplicationFactory<Startup>>
    {
    private readonly CustomWebApplicationFactory<Startup> _webApplicationFactory;
    private readonly ITestOutputHelper _testOutput;
    private readonly HttpClient _httpClient;
    private readonly MyDbContext _myDbContext;

    public IdpUserServiceTests(CustomWebApplicationFactory<Startup> webApplicationFactory, MyDbContext myDbContext, ITestOutputHelper testOutput)
        {
        _webApplicationFactory = webApplicationFactory;
        _myDbContext = myDbContext;
        _testOutput = testOutput;
        _httpClient = _webApplicationFactory.CreateClient();
        }

    //Tests 

but in attempting to run a test, I get the following error:

The following constructor parameters did not have matching fixture data: MyDbContext objMyDbContext

I'm looking for the correct way to access the in-memory database - it's obviously not via constructor injection. I've had a go with this answer - Access in memory dbcontext in integration test - but things seem to have changed between 2.2 and 3.1.

Mcginty

Answer 1

It turned out that the Access in memory dbcontext in integration test answer referenced above was not quite right for ASP.NET Core 3.1. The scopeFactory has to be found from a different source:

var scopeFactory = _webApplicationFactory.Services.GetService<IServiceScopeFactory>();

So the test class now looks like:

public class ServiceTests : IClassFixture<CustomWebApplicationFactory<Startup>>
    {
    private readonly CustomWebApplicationFactory<Startup> _webApplicationFactory;
    private readonly ITestOutputHelper _testOutput;
    private readonly HttpClient _httpClient;

    public ServiceTests(CustomWebApplicationFactory<Startup> webApplicationFactory, ITestOutputHelper testOutput)
        {
        _webApplicationFactory = webApplicationFactory;
        _testOutput = testOutput;
        _httpClient = _webApplicationFactory.CreateClient();
        }

    [Fact]

    public async Task AServiceTest()
        {
        // Do some HTTP client stuff that alters the in-memory database

      var scopeFactory = _webApplicationFactory.Services.GetService<IServiceScopeFactory>();

        using(var scope = scopeFactory.CreateScope())
            {
            var myDataContext = scope.ServiceProvider.GetService<MyDataContext>();

            // Query the in-memory database
            }
        }
    }

Mcginty