EntityFramework、DbContextScope 和 Effort - 异常：DbContext 已在单元测试中处理

Question

我正在尝试为服务层编写单元测试（使用 NUnit），它使用：

1. 实体框架作为数据访问层
2. DbContextScope 用于管理 DbContext 生命周期

我还使用 Effort.EF6 在单元测试中模拟 DbContext。不幸的是，我无法找到一种方法使 DbContextScope 与 Effort 兼容，以便我可以正确测试所有情况。

---

代码概述

服务层由执行一些业务逻辑的类（服务）组成。每个方法都被视为一个完整的事务，以

context.SaveChanges()

结束。示例：

    private IDbContextScopeFactory _dbContextScopeFactory;

    public DepartmentsService(IDbContextScopeFactory dbContextScopeFactory)
    {
        _dbContextScopeFactory = dbContextScopeFactory;
    }

    public BusinessModel.Department Insert(BusinessModel.Department department)
    {
        using (var dbContextScope = _dbContextScopeFactory.Create())
        {
            // Validation
            ValidateAndThrowOnFailure(department, new DepartmentAddValidator());

            // Operation
            DBModel.Department newDepartment = Mapper.Map<DBModel.Department>(department);

            newDepartment.InsertDateUTC = DateTime.UtcNow;

            dbContextScope.DbContexts.Get<DPSContext>().Departments.Add(newDepartment);
            dbContextScope.SaveChanges();

            return Mapper.Map<BusinessModel.Department>(newDepartment);
        }
    }

为了对这种方法进行单元测试，我在每次测试之前都会做一些准备：

    private IDepartmentsService _departmentsService;
    private IDbContextScopeFactory _dbContextScopeFactory;
    private IDbContextFactory _dbContextFactory;
    private DBModel.DPSContext _dbEntities;

    [SetUp]
    public void ReInitializeTest()
    {
        // Setup DbContext with Effort.EF6
        string connStr = ConfigurationManager.ConnectionStrings["DPSContext"].ConnectionString;
        DbConnection connection = EntityConnectionFactory.CreateTransient(connStr);
        _dbEntities = new DBModel.DPSContext(connection);

        // Fill DbContext with in-memory data
        _dbEntities.Departments.AddRange(DataInitializer.GetDepartments());
        _dbEntities.SaveChanges();

        // Mock IDbContextFactory so that it returns in-memory context
        var contextFactoryMock = new Mock<IDbContextFactory>();

        contextFactoryMock
            .Setup(f => f.CreateDbContext<DBModel.DPSContext>())
            .Returns(_dbEntities);

        _dbContextFactory = contextFactoryMock.Object;

        // Setup DbContextScopeFactory to use mocked context
        _dbContextScopeFactory = new DbContextScopeFactory(_dbContextFactory);
        _departmentsService = new DepartmentsService(_dbContextScopeFactory);
    }

---

测试和问题

这是一个简单的单元测试：

    [Test]
    public void Insert_WhenValidModelPassed_ShouldInsertNewRecord()
    {
        // Given
        BusinessModel.Department newDepartment = DataInitializer.GetExampleOfNewDepartment();

        // When
        _departmentsService.Insert(newDepartment);

        // Then
        Assert.AreEqual(3, _dbEntities.Departments.Count());
    }

问题是测试失败并出现异常：

System.InvalidOperationException : The operation cannot be completed because the DbContext has been disposed.

似乎在

Insert

方法内部使用的 DbContextScope 在

using

块的末尾处处理分配的上下文，因此

Assert

在调用时会抛出异常。有没有人遇到过类似的问题，或者只是知道我应该做什么来成功测试这个和类似的场景？

Answer 1

对于遇到类似问题的任何人，我创建了一个有点脏但有效的解决方案（至少我希望如此）。除了我在问题中写的内容之外，我还创建了一个从真实上下文派生的类，并使

Dispose

方法不执行任何操作。我还添加了一个

RealDispose

方法，该方法在每次测试结束时调用。

    public class TestableDPSContext : DBModel.DPSContext
    {
        public TestableDPSContext(DbConnection connection)
            : base(connection)
        {

        }

        protected override void Dispose(bool disposing)
        {
            // Do nothing
        }

        public void RealDispose(bool disposing)
        {
            // Invoke real dispose
            base.Dispose(disposing);
        }
    }

    [TearDown]
    public void FinishTest()
    {
        _dbEntities.RealDispose(false);
    }

也许有更好的解决方案，但目前似乎解决了

DbContext

在测试中过早处置的问题。

Answer 2

这是我的“XUnit + EF Core”版本，非常有用的 PJDev 答案：

public class TestableAppDbContext: AppDbContext
{
    public TestableAppDbContext(DbContextOptions<AppDbContext> options)
        : base(options)
    {
    }

    public override void Dispose()
    {
        // Do nothing
    }

    public override ValueTask DisposeAsync()
    {
        // Do nothing
        return ValueTask.CompletedTask;
    }

    public void RealDispose()
    {
        // Invoke real dispose
        base.Dispose();
    }

    public ValueTask RealDisposeAsync()
    {
        // Invoke real dispose
        return base.DisposeAsync();
    }
}