最近团队有小伙伴问在单元测试中如何Mock HttpContext. 这是一个好问题，整理了一个实现方案分享给大家。

在C#中，尤其是在单元测试场景下，模拟（Mocking）HttpContext 是一种常见的做法。这允许我们在没有实际HTTP请求的情况下测试与HTTP上下文相关的代码。

为了模拟HttpContext，我们通常会使用像Moq这样的库，它是.NET中一个流行的模拟框架。
以下是一个简单的示例，展示了如何使用Moq来模拟一个HttpContext：
首先，你需要安装Moq库。如果你使用的是.NET Core或.NET 5/6/7/8等较新版本，你可以通过NuGet包管理器来安装它：

dotnet add package Moq

或者，在Visual Studio中，你可以通过NuGet包管理器UI来搜索并安装Moq。

安装完成后，编写以下代码来创建一个模拟的HttpContext.

usingSystem.Security.Claims;usingSystem.Web;usingMoq;//创建一个模拟的HttpContext
var mockContext = new Mock<HttpContextBase>();//模拟HttpRequest
var mockRequest = new Mock<HttpRequestBase>();

mockRequest.Setup(r=> r.ApplicationPath).Returns("/");

mockRequest.Setup(r=> r.ServerVariables).Returns(newSystem.Collections.Specialized.NameValueCollection());

mockContext.Setup(c=>c.Request).Returns(mockRequest.Object);//模拟HttpResponse
var mockResponse = new Mock<HttpResponseBase>();

mockResponse.Setup(r=> r.Cache).Returns(newHttpCachePolicyBase());

mockContext.Setup(c=>c.Response).Returns(mockResponse.Object);//模拟HttpSessionState
var mockSession = new Mock<HttpSessionStateBase>();

mockSession.Setup(s=> s["MySessionItem"]).Returns("SessionValue");

mockContext.Setup(c=>c.Session).Returns(mockSession.Object);//模拟HttpServerUtility
var mockServer = new Mock<HttpServerUtilityBase>();

mockContext.Setup(c=>c.Server).Returns(mockServer.Object);//模拟HttpUser
var mockUser = new Mock<IPrincipal>();var mockIdentity = new Mock<IIdentity>();

mockIdentity.Setup(i=> i.Name).Returns("User");

mockIdentity.Setup(i=> i.IsAuthenticated).Returns(true);

mockUser.Setup(u=>u.Identity).Returns(mockIdentity.Object);

mockContext.Setup(c=>c.User).Returns(mockUser.Object);//现在你可以使用 mockContext.Object 来作为你的HttpContextBase对象了
var httpContext =mockContext.Object;//使用示例：
var userName = httpContext.User.Identity.Name; //返回 "User"
var isAuthenticated = httpContext.User.Identity.IsAuthenticated; //返回 true
var mySessionItem = httpContext.Session["MySessionItem"]; //返回 "SessionValue"

更进一步，我们可以把这个HttpContext的mock封装成一个服务，团队其他的小伙伴也可以一起使用。

so，为了使其更加模块化和可重用，我们可以将这些模拟的创建过程封装到一个方法中，或者创建一个专门的服务类来提供
HttpContextBase
的模拟实例。

usingSystem.Collections.Specialized;usingSystem.Security.Principal;usingSystem.Web;usingMoq;public static classMockHttpContextService

{public staticHttpContextBase CreateMockHttpContext(string userName = "User",bool isAuthenticated = true,string sessionKey = "MySessionItem",object sessionValue = null,string applicationPath = "/",

        NameValueCollection serverVariables= null)

    {var mockContext = new Mock<HttpContextBase>();//模拟HttpRequest
        var mockRequest = new Mock<HttpRequestBase>();

        mockRequest.Setup(r=>r.ApplicationPath).Returns(applicationPath);

        mockRequest.Setup(r=> r.ServerVariables).Returns(serverVariables ?? newNameValueCollection());

        mockContext.Setup(c=>c.Request).Returns(mockRequest.Object);//模拟HttpResponse
        var mockResponse = new Mock<HttpResponseBase>();

        mockResponse.Setup(r=> r.Cache).Returns(newHttpCachePolicyBase());

        mockContext.Setup(c=>c.Response).Returns(mockResponse.Object);//模拟HttpSessionState
        var mockSession = new Mock<HttpSessionStateBase>();if (sessionKey != null)

        {

            mockSession.Setup(s=>s[sessionKey]).Returns(sessionValue);

        }

        mockContext.Setup(c=>c.Session).Returns(mockSession.Object);//模拟HttpServerUtility
        var mockServer = new Mock<HttpServerUtilityBase>();

        mockContext.Setup(c=>c.Server).Returns(mockServer.Object);//模拟HttpUser
        var mockUser = new Mock<IPrincipal>();var mockIdentity = new Mock<IIdentity>();

        mockIdentity.Setup(i=>i.Name).Returns(userName);

        mockIdentity.Setup(i=>i.IsAuthenticated).Returns(isAuthenticated);

        mockUser.Setup(u=>u.Identity).Returns(mockIdentity.Object);

        mockContext.Setup(c=>c.User).Returns(mockUser.Object);returnmockContext.Object;

    }

}

创建模拟
HttpContext
对象时传入自定义参数：

var httpContext =MockHttpContextService.CreateMockHttpContext(

    userName:"CustomUser",

    isAuthenticated:false,

    sessionKey:"CustomSessionItem",

    sessionValue:"CustomSessionValue",

    applicationPath:"/MyApp",

    serverVariables:new NameValueCollection { { "SERVER_NAME", "localhost"} }

);//使用示例：
var userName = httpContext.User.Identity.Name; //返回 "CustomUser"
var isAuthenticated = httpContext.User.Identity.IsAuthenticated; //返回 false
var mySessionItem = httpContext.Session["CustomSessionItem"]; //返回 "CustomSessionValue"
var appPath = httpContext.Request.ApplicationPath; //返回 "/MyApp"
var serverName = httpContext.Request.ServerVariables["SERVER_NAME"]; //返回 "localhost"

以上是单元测试中如何Mock HttpContext的分享，希望能帮助到大家。

周国庆

2024/1/24

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