unit-testing - 使用服务定位器时如何为 ActionFilter 编写单元测试

Question

我打算写一个 ActionFilter用于业务验证，其中一些服务将通过服务定位器解决(我知道这不是一个好的做法，我尽可能避免使用服务定位器模式，但在这种情况下我想使用它)。
OnActionExecuting过滤器的方法是这样的:

    public override void OnActionExecuting(ActionExecutingContext actionContext)
    {
        // get validator for input;
        var validator = actionContext.HttpContext.RequestServices.GetService<IValidator<TypeOfInput>>();// i will ask another question for this line
        if(!validator.IsValid(input))
        {
            //send errors
        }
    }

是否可以为上述 ActionFilter 编写单元测试如何？

Answer 1

这是一个关于如何创建模拟(使用 XUnit 和 Moq 框架)来验证 IsValid 的示例。方法被调用并且模拟返回 false .

using Dealz.Common.Web.Tests.Utils;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Mvc.Filters;
using Microsoft.Extensions.DependencyInjection;
using Moq;
using System;
using Xunit;

namespace Dealz.Common.Web.Tests.ActionFilters
{
    public class TestActionFilter
    {
        [Fact]
        public void ActionFilterTest()
        {
            /****************
             * Setup
             ****************/

            // Create the userValidatorMock
            var userValidatorMock = new Mock<IValidator<User>>();
            userValidatorMock.Setup(validator => validator
                // For any parameter passed to IsValid
                .IsValid(It.IsAny<User>())
            )
            // return false when IsValid is called
            .Returns(false)
            // Make sure that `IsValid` is being called at least once or throw error
            .Verifiable();

            // If provider.GetService(typeof(IValidator<User>)) gets called, 
            // IValidator<User> mock will be returned
            var serviceProviderMock = new Mock<IServiceProvider>();
            serviceProviderMock.Setup(provider => provider.GetService(typeof(IValidator<User>)))
                .Returns(userValidatorMock.Object);

            // Mock the HttpContext to return a mockable 
            var httpContextMock = new Mock<HttpContext>();
            httpContextMock.SetupGet(context => context.RequestServices)
                .Returns(serviceProviderMock.Object);


            var actionExecutingContext = HttpContextUtils.MockedActionExecutingContext(httpContextMock.Object, null);

            /****************
             * Act
             ****************/
            var userValidator = new ValidationActionFilter<User>();
            userValidator.OnActionExecuting(actionExecutingContext);

            /****************
             * Verify
             ****************/

            // Make sure that IsValid is being called at least once, otherwise this throws an exception. This is a behavior test
            userValidatorMock.Verify();

            // TODO: Also Mock HttpContext.Response and return in it's Body proeprty a memory stream where 
            // your ActionFilter writes to and validate the input is what you desire.
        }
    }

    class User
    {
        public string Username { get; set; }
    }

    class ValidationActionFilter<T> : IActionFilter where T : class, new()
    {
        public void OnActionExecuted(ActionExecutedContext context)
        {
            throw new NotImplementedException();
        }

        public void OnActionExecuting(ActionExecutingContext actionContext)
        {
            var type = typeof(IValidator<>).MakeGenericType(typeof(T));

            var validator = (IValidator<T>)actionContext.HttpContext
                .RequestServices.GetService<IValidator<T>>();

            // Get your input somehow
            T input = new T();

            if (!validator.IsValid(input))
            {
                //send errors
                actionContext.HttpContext.Response.WriteAsync("Error");
            }
        }
    }

    internal interface IValidator<T>
    {
        bool IsValid(T input);
    }
}

HttpContextUtils.cs

using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.Mvc.Filters;
using System.Collections.Generic;

namespace Dealz.Common.Web.Tests.Utils
{
    public class HttpContextUtils
    {
        public static ActionExecutingContext MockedActionExecutingContext(
            HttpContext context,
            IList<IFilterMetadata> filters,
            IDictionary<string, object> actionArguments,
            object controller
        )
        {
            var actionContext = new ActionContext() { HttpContext = context };

            return new ActionExecutingContext(actionContext, filters, actionArguments, controller);
        }
        public static ActionExecutingContext MockedActionExecutingContext(
            HttpContext context,
            object controller
        )
        {
            return MockedActionExecutingContext(context, new List<IFilterMetadata>(), new Dictionary<string, object>(), controller);
        }
    }
}

如您所见，这相当困惑，您需要创建大量模拟来模拟实际类的不同响应，才能单独测试 ActionAttribute。