c# - 对上传文件的 Web API 端点进行单元测试

Question

我有一个要进行单元测试的 Web API 端点。我有一个自定义 SwaggerUploadFile 属性，允许在 swagger 页面上使用文件上传按钮。但是对于单元测试，我不知道如何传入文件。

对于单元测试，我使用的是:Xunit、Moq 和 Fluent Assertions

下面是我的 Controller 和端点:

public class MyAppController : ApiController
{
    private readonly IMyApp _myApp;

    public MyAppController(IMyApp myApp)
    {
         if (myApp == null) throw new ArgumentNullException(nameof(myApp));
         _myApp = myApp;
    }

    [HttpPost]
    [ResponseType(typeof(string))]
    [Route("api/myApp/UploadFile")]
    [SwaggerUploadFile("myFile", "Upload a .zip format file", Required = true, Type = "file")]
    public async Task<IHttpActionResult> UploadFile()
    {
        if (!Request.Content.IsMimeMultipartContent())
        {
            throw new HttpResponseException(HttpStatusCode.UnsupportedMediaType);
        }

        var provider = await Request.Content.ReadAsMultipartAsync();
        var bytes = await provider.Contents.First().ReadAsByteArrayAsync();
        try
        {
           var retVal = _myApp.CheckAndSaveByteStreamAsync(bytes).Result;
           if(retVal)
            {
                return
                    ResponseMessage(
                        new HttpResponseMessage(HttpStatusCode.OK)
                        {
                            Content = new StringContent(JsonConvert.SerializeObject(
                                new WebApiResponse
                                {
                                    Message = "File has been saved"
                                }), Encoding.UTF8, "application/json")
                        });
            }             
            return ResponseMessage(
                new HttpResponseMessage(HttpStatusCode.BadRequest)
                {
                    Content = new StringContent(JsonConvert.SerializeObject(
                        new WebApiResponse
                        {
                            Message = "The file could not be saved"
                        }), Encoding.UTF8, "application/json")
                });
        }
        catch (Exception e)
        {
            //log error
            return BadRequest("Oops...something went wrong");
        }
    }    
}

我到目前为止的单元测试:

    [Fact]
    [Trait("Category", "MyAppController")]
    public void UploadFileTestWorks()
    {
        //Arrange

        _myApp.Setup(x => x.CheckAndSaveByteStreamAsync(It.IsAny<byte[]>())).ReturnsAsync(() => true);
        var expected = JsonConvert.SerializeObject(
            new WebApiResponse
            {
                Message = "The file has been saved"
            });

        var _sut = new MyAppController(_myApp.Object);


        //Act
        var retVal = _sut.UploadFile();
        var content = (ResponseMessageResult)retVal.Result;
        var contentResult = content.Response.Content.ReadAsStringAsync().Result;
        //Assert
        contentResult.Should().Be(expected); 
    }

上面的代码失败了，因为当它到达这一行 if(!Request.Content.IsMimeMultipartContent()) 我们得到一个 NullReferenceException > "{"Object reference未设置为对象的实例。"}"

已实现最佳答案:

创建了一个接口(interface):

 public interface IApiRequestProvider
    {
        Task<MultipartMemoryStreamProvider> ReadAsMultiPartAsync();

        bool IsMimeMultiPartContent();
    }

然后是一个实现:

public class ApiRequestProvider : ApiController, IApiRequestProvider
    {       
        public Task<MultipartMemoryStreamProvider> ReadAsMultiPartAsync()
        {
            return Request.Content.ReadAsMultipartAsync();
        }
        public bool IsMimeMultiPartContent()
        {
            return Request.Content.IsMimeMultipartContent();
        }
    }

现在我的 Controller 使用构造函数注入(inject)来获取 RequestProvider:

 private readonly IMyApp _myApp;
 private readonly IApiRequestProvider _apiRequestProvider;

 public MyAppController(IMyApp myApp, IApiRequestProvider apiRequestProvider)
        {
             if (myApp == null) throw new ArgumentNullException(nameof(myApp));
             _myApp = myApp;

             if (apiRequestProvider== null) throw new ArgumentNullException(nameof(apiRequestProvider));
             _apiRequestProvider= apiRequestProvider;
        }

方法的新实现:

[HttpPost]
        [ResponseType(typeof(string))]
        [Route("api/myApp/UploadFile")]
        [SwaggerUploadFile("myFile", "Upload a .zip format file", Required = true, Type = "file")]
        public async Task<IHttpActionResult> UploadFile()
        {
            if (!_apiRequestProvider.IsMimeMultiPartContent())
            {
                throw new HttpResponseException(HttpStatusCode.UnsupportedMediaType);
            }

            var provider = await _apiRequestProvider.ReadAsMultiPartAsync();
            var bytes = await provider.Contents.First().ReadAsByteArrayAsync();
            try
            {
               var retVal = _myApp.CheckAndSaveByteStreamAsync(bytes).Result;
               if(retVal)
                {
                    return
                        ResponseMessage(
                            new HttpResponseMessage(HttpStatusCode.OK)


             {
                            Content = new StringContent(JsonConvert.SerializeObject(
                                new WebApiResponse
                                {
                                    Message = "File has been saved"
                                }), Encoding.UTF8, "application/json")
                        });
            }             
            return ResponseMessage(
                new HttpResponseMessage(HttpStatusCode.BadRequest)
                {
                    Content = new StringContent(JsonConvert.SerializeObject(
                        new WebApiResponse
                        {
                            Message = "The file could not be saved"
                        }), Encoding.UTF8, "application/json")
                });
        }
        catch (Exception e)
        {
            //log error
            return BadRequest("Oops...something went wrong");
        }
    }    
}

我的模拟 ApiController 请求的单元测试:

    [Fact]
    [Trait("Category", "MyAppController")]
    public void UploadFileTestWorks()
    {
        //Arrange
        _apiRequestProvider = new Mock<IApiRequestProvider>();
        _myApp = new Mock<IMyApp>();
         MultipartMemoryStreamProvider fakeStream = new MultipartMemoryStreamProvider();
        fakeStream.Contents.Add(CreateFakeMultiPartFormData());
        _apiRequestProvider.Setup(x => x.IsMimeMultiPartContent()).Returns(true);
        _apiRequestProvider.Setup(x => x.ReadAsMultiPartAsync()).ReturnsAsync(()=>fakeStream);
        _myApp.Setup(x => x.CheckAndSaveByteStreamAsync(It.IsAny<byte[]>())).ReturnsAsync(() => true);
        var expected = JsonConvert.SerializeObject(
            new WebApiResponse
            {
                Message = "The file has been saved"
            });

        var _sut = new MyAppController(_myApp.Object, _apiRequestProvider.Object);

        //Act
        var retVal = _sut.UploadFile();
        var content = (ResponseMessageResult)retVal.Result;
        var contentResult = content.Response.Content.ReadAsStringAsync().Result;
        //Assert
        contentResult.Should().Be(expected); 
    }

感谢@Badulake 的想法

Answer 1

你应该在方法的逻辑上做一个更好的分离。 重构您的方法，使其不依赖于与您的 Web 框架相关的任何类，在本例中为 Request 类。您的上传代码不需要知道任何关于它的信息。 作为提示:

var provider = await Request.Content.ReadAsMultipartAsync();

可以转化为:

var provider = IProviderExtracter.Extract();

public interface IProviderExtracter
{
    Task<provider> Extract();
}

public class RequestProviderExtracter:IProviderExtracter
{
    public Task<provider> Extract()
    { 
      return Request.Content.ReadAsMultipartAsync();
    }
}

在您的测试中，您可以轻松模拟 IProviderExtracter 并专注于执行代码的每个部分的工作。

想法是您获得最解耦的代码，因此您的担心只集中在模拟您开发的类上，而不是框架强制您使用的类。