1. 创建一个ASP.NET Core Web API项目。使用以下代码将WebApplicationFactory注入ServiceCollection：

services.AddControllers();

services.AddDbContext(options =>
    options.UseInMemoryDatabase(databaseName: "TestDb"));

services.AddScoped();

services.AddAutoMapper(typeof(MyProfile).Assembly);

services.AddMvc()
    .AddApplicationPart(typeof(Startup).Assembly)
    .AddControllersAsServices();
    
services.AddHttpContextAccessor();

services.AddAuthentication("Test")
    .AddScheme("Test", options => { });

services.AddAuthorization(options =>
{
    options.AddPolicy("Policy",
        policy => policy.Requirements.Add(new TestRequirement()));
});

2. 创建MockWebApplicationFactory，继承WebApplicationFactory，并重写ConfigureWebHost方法，为测试提供一个数据库：

public class MockWebApplicationFactory : WebApplicationFactory
{
    protected override void ConfigureWebHost(IWebHostBuilder builder)
    {
        builder.ConfigureServices(services =>
        {
            var descriptor = services.SingleOrDefault(
                d => d.ServiceType ==
                    typeof(DbContextOptions));

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

            services.AddDbContext(options =>
            {
                options.UseInMemoryDatabase("TestDb");
            });

            services.AddScoped();
        });
    }
}

3. 创建MockMyService，一个伪造的服务类，实现IMyService接口，以便在某些情况下更好地控制端点的行为：

public class MockMyService : IMyService
{
    public string GetMyString()
    {
        return "Mock string";
    }
}

4. 编写测试用例：

public class MyControllerTests : IClassFixture
{
    private readonly MockWebApplicationFactory _factory;

    public MyControllerTests(MockWebApplicationFactory factory)
    {
        _factory = factory;
    }

    [Fact]
    public async Task GetMyString_ReturnsCorrectString()
    {
        var client = _factory.CreateClient();

        var response = await client.GetAsync("/api