Net Core：集成测试中的依赖注入

Question

集成测试中如何进行依赖注入？调用departmentRepository或departmentAppService，会给我带来null下面的错误。

public class DepartmentAppServiceTest
{
    public SharedServicesContext context;
    public IMapper mapper;
    public IRepository<Department, int> departmentRepository;
    public IDepartmentAppService departmentAppService;

    public DepartmentAppServiceTest()
    {
        ServiceCollection services = new ServiceCollection();
        services.AddTransient<IRepository<Department>, BaseRepository<Department>>();
        services.AddTransient<IDepartmentAppService, DepartmentAppService>();

调试和设置断点，调用此存储库或应用程序服务均为空，

新方法

 [Fact]
 var departmentDto = await departmentAppService.GetDepartmentById(2);

应用服务的构造函数

DepartmentAppService(departmentRepository, mapper)
DepartmentRepository(dbcontext)

错误：

消息：System.NullReferenceException：未将对象引用设置为对象的实例。

Answer 1

对于我们的集成测试，我们以编程方式启动应用程序并使用 HttpClient 对 API 端点进行调用。这样您的应用程序就会运行整个启动过程，并且依赖项注入就像一个魅力。

这是服务器启动和客户端创建的示例，它可以重复用于多个测试：

_server = new TestServer(new WebHostBuilder()
                .UseEnvironment("Testing")
                .UseContentRoot(applicationPath)
                .UseConfiguration(new ConfigurationBuilder()
                    .SetBasePath(applicationPath)
                    .AddJsonFile("appsettings.json")
                    .AddJsonFile("appsettings.Testing.json")
                    .Build()
                )
                .UseStartup<TestStartup>());
_client = _server.CreateClient();
// Act
var response = await _client.GetAsync("/");

// Assert
response.EnsureSuccessStatusCode();

微软也通过 HttpClient 对此进行了记录：
https://learn.microsoft.com/en-us/aspnet/core/test/integration-tests ?view=aspnetcore-2.2