使用WebApplicationFactory测试时，app.Run带URL参数引发异常的解决

问题原因 #

测试时WebApplicationFactory默认使用TestServer，而TestServer初始化时不会自动添加IServerAddressesFeature，直接调用带URL参数的app.Run()会触发找不到该Feature的异常。

方案1：根据环境条件分支运行 #

在服务的Program.cs中判断运行环境，测试环境下调用无参数的app.Run()，避免指定URL：

public static void Main(string[] args)
{
    var builder = WebApplication.CreateBuilder(args);

    var startup = new Startup(builder.Configuration);
    startup.ConfigureServices(builder.Services);

    var app = builder.Build();

    startup.Configure(app);

    // 识别测试环境，分支执行
    if (builder.Environment.IsEnvironment("Test"))
    {
        app.Run();
    }
    else
    {
        app.Run("http://+:5202");
    }
}

测试代码中指定测试环境：

public ServiceController_should(WebApplicationFactory<Startup> factory)
{
    _client = factory
        .WithWebHostBuilder(builder =>
        {
            builder.UseEnvironment("Test");
            builder.ConfigureServices(services =>
            {
                // 自定义DI配置
            });
        })
        .CreateClient();
}

方案2：给TestServer手动添加IServerAddressesFeature #

在测试的WebHost配置中，手动注入IServerAddressesFeature，让app.Run()能找到对应的Feature：

public ServiceController_should(WebApplicationFactory<Startup> factory)
{
    _client = factory
        .WithWebHostBuilder(builder =>
        {
            builder.ConfigureServices(services =>
            {
                // 自定义DI配置
            });
            // 给TestServer添加地址Feature
            builder.ConfigureTestServices(services =>
            {
                services.PostConfigure<TestServerOptions>(options =>
                {
                    options.Features.Set<IServerAddressesFeature>(new ServerAddressesFeature
                    {
                        Addresses = { "http://+:5202" }
                    });
                });
            });
        })
        .CreateClient();
}

方案3：通过配置文件管理URL #

把URL从硬编码改为从配置读取，测试时可灵活覆盖配置：

1. 在服务的appsettings.json中添加URL配置：

{
  "Urls": "http://+:5202"
}

2. 修改Program.cs的Main方法：

public static void Main(string[] args)
{
    var builder = WebApplication.CreateBuilder(args);

    var startup = new Startup(builder.Configuration);
    startup.ConfigureServices(builder.Services);

    var app = builder.Build();

    startup.Configure(app);

    // 从配置读取URL，无配置则用默认
    var url = builder.Configuration["Urls"];
    if (!string.IsNullOrEmpty(url))
    {
        app.Run(url);
    }
    else
    {
        app.Run();
    }
}

3. 测试时覆盖配置：

public ServiceController_should(WebApplicationFactory<Startup> factory)
{
    _client = factory
        .WithWebHostBuilder(builder =>
        {
            builder.ConfigureAppConfiguration(config =>
            {
                config.AddInMemoryCollection(new Dictionary<string, string>
                {
                    { "Urls", "" } // 测试时清空URL配置
                });
            });
            builder.ConfigureServices(services =>
            {
                // 自定义DI配置
            });
        })
        .CreateClient();
}

内容的提问来源于stack exchange，提问作者Puddleofpandas