WebAPI的一种单元测试方案

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原文出处： richieyangs   

大家是如何对webApi写测试的呢？
1.利用Fiddler直接做请求，观察response的内容。
2.利用Httpclient做请求，断言response的内容。
3.直接调用webApi的action,这种方式的测试跟真实的调用还是有一定差距，不够完美。

接下来我介绍一种webApi的in-memory调用方法，也能够达到对webApi的测试，并且由于是in-memory调用，效率也比较高，非常适写单元测试。本文参考了In memory client, host and integration testing of your Web API service。

一、首先写一个OrderController用来做测试用

C#

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public class OrderController : ApiController     {         // GET api/order         public Order Get()         {             return new Order(){Id = 1,Descriptions = 'descriptions',Name = 'name'};         }         // GET api/order/5         public string Get(int id)         {             return 'value';         }         // POST api/order         public Order Post(Order order)         {             return order;         }         // DELETE api/order/5         public void Delete(int id)         {         }     }

二、WebApi的请求过程

webApi的核心是对消息的管道处理，整个核心是有一系列消息处理器(HttpMessageHandler)首尾连接的双向管道，管道头为HttpServer,管道尾为HttpControllerDispatcher,HttpControllerDispatcher负责对controller的激活和action的执行，然后相应的消息逆向流出管道。

所以我们可以利用HttpMessageInvoker将一个请求消息HttpRequestMessage发送到管道中，最后收到的消息HttpResponseMessage就代表一个真实的请求响应。

三、Get请求的测试

C#

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[Test]         public void GetTest()         {             string baseAddress = 'http://localhost:33203/';             HttpConfiguration config = new HttpConfiguration();             WebApiConfig.Register(config);             config.IncludeErrorDetailPolicy = IncludeErrorDetailPolicy.Always;             HttpServer server = new HttpServer(config);             HttpMessageInvoker messageInvoker = new HttpMessageInvoker(server);             CancellationTokenSource cts = new CancellationTokenSource();             HttpRequestMessage request = new HttpRequestMessage(HttpMethod.Get, baseAddress + 'api/order');             using (HttpResponseMessage response = messageInvoker.SendAsync(request, cts.Token).Result)             {                 var content = response.Content.ReadAsStringAsync().Result;                 var result = JsonConvert.DeserializeObject(content);                 result.Name.Should().Be('name');             }         }

四、Post请求的测试

C#

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[Test]         public void PostTest()         {             string baseAddress = 'http://localhost:33203/';             HttpConfiguration config = new HttpConfiguration();             WebApiConfig.Register(config);             config.IncludeErrorDetailPolicy = IncludeErrorDetailPolicy.Always;             HttpServer server = new HttpServer(config);             HttpMessageInvoker messageInvoker = new HttpMessageInvoker(server);             CancellationTokenSource cts = new CancellationTokenSource();             HttpRequestMessage request = new HttpRequestMessage(HttpMethod.Post, baseAddress + 'api/order');             var order = new Order() { Id = 1, Name = 'orderName', Descriptions = 'orderDescriptions' };             request.Content = new ObjectContent(order, new JsonMediaTypeFormatter());             using (HttpResponseMessage response = messageInvoker.SendAsync(request, cts.Token).Result)             {                 var content = JsonConvert.SerializeObject(order, new JsonSerializerSettings() { ContractResolver = new CamelCasePropertyNamesContractResolver() });                 response.Content.ReadAsStringAsync().Result.Should().Be(content);             }         }

四、重构

可以看到这两个测试大部分的代码是相同的，都是用来发送请求。因此我们提取一个webApiTestBase类，该基类可以提供InvokeGetRequest,InvokePostRequest,InvokePutRequest等方法

C#

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public abstract class ApiTestBase     {         public abstract string GetBaseAddress();         protected TResult InvokeGetRequest(string api)         {             using (var invoker = CreateMessageInvoker())             {                 using (var cts = new CancellationTokenSource())                 {                     var request = new HttpRequestMessage(HttpMethod.Get, GetBaseAddress() + api);                     using (HttpResponseMessage response = invoker.SendAsync(request, cts.Token).Result)                     {                         var result = response.Content.ReadAsStringAsync().Result;                         return JsonConvert.DeserializeObject(result);                     }                 }             }         }         protected TResult InvokePostRequest(string api, TArguemnt arg)         {             var invoker = CreateMessageInvoker();             using (var cts = new CancellationTokenSource())             {                 var request = new HttpRequestMessage(HttpMethod.Post, GetBaseAddress() + api);                 request.Content = new ObjectContent(arg, new JsonMediaTypeFormatter());                 using (HttpResponseMessage response = invoker.SendAsync(request, cts.Token).Result)                 {                     var result = response.Content.ReadAsStringAsync().Result;                     return JsonConvert.DeserializeObject(result);                 }             }         }         private HttpMessageInvoker CreateMessageInvoker()         {             var config = new HttpConfiguration();             WebApiConfig.Register(config);             var server = new HttpServer(config);             var messageInvoker = new HttpMessageInvoker(server);             return messageInvoker;         }     }

有了这个基类，我们写测试只需要重写方法GetBaseAddress()，然后直接调用基类方法并进行断言即可

C#

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[TestFixture]     public class OrderApiTests:ApiTestBase     {         public override string GetBaseAddress()         {             return 'http://localhost:33203/';         }         [Test]         public void Should_get_order_successfully()         {             var result = InvokeGetRequest('api/order');             result.Name.Should().Be('name');             result.Descriptions.Should().Be('descriptions');             result.Id.Should().Be(1);         }         [Test]         public void Should_post_order_successfully()         {             var newOrder=new Order(){Name = 'newOrder',Id = 100,Descriptions = 'new-order-description'};             var result = InvokePostRequest('api/order', newOrder);             result.Name.Should().Be('newOrder');             result.Id.Should().Be(100);             result.Descriptions.Should().Be('new-order-description');         }     }

是不是干净多了。

这种in-memory的测试方案有什么优点和缺点呢？

优点：
1.模拟真实调用，需要传入api地址即可得到结果，由于整个调用是in-memory的，所有效率很高，很适合集成测试。
2.整个测试时可以调试的，可以直接从单元测试调试进去，如果你写一个httpClient的测试，需要把webApi启动起来，然后。。。麻烦

缺点：我觉得原文作者说的那些缺点都可以忽略不计。

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