如何在 EFCore 中模拟 EntityEntry

Question

我正在尝试为处理异常并重新加载 Entity Framework Core 中的实体的方法编写单元测试。该方法包含以下代码：

    catch (DbUpdateConcurrencyException)
    {
        await context.Entry(myEntityInstance).ReloadAsync();
    }
    catch { return null; };

我已成功模拟

SaveChangesAsync

并抛出所需的异常。但是，我在尝试模拟

Entry

方法时遇到了问题：

    contextMock.Setup(c => c.Entry(It.IsAny<MyEntity>()).ReloadAsync(default))

这会导致 ArgumentException：

Can not instantiate proxy of class: Microsoft.EntityFrameworkCore.ChangeTracking.EntityEntry ...
Could not find a parameterless constructor. (Parameter 'constructorArguments') ---> System.MissingMethodException: Constructor on type 'Castle.Proxies.EntityEntry`1Proxy' not found.

问题是

EntityEntry<TEntity>

不是模拟友好的，因为它只有一个构造函数：

[EntityFrameworkInternal]
public EntityEntry(InternalEntityEntry internalEntry)

InternalEntityEntry

是一个内部 EF Core 类，它依赖于其他内部类的实例。有一个 GitHub 问题 Trouble Mocking EntityEntry 讨论了这个问题，但 EF 团队似乎不打算进行任何更改。

如何在

EF Core

中模拟 EntityEntry 来有效测试此方法？

Answer 1

彻底检查

EF Core

源代码后，我创建了以下方法来模拟

EntityEntry

。该方法严重依赖内部API，但避免了反射。如果未来发生重大变化，可以轻松识别并纠正测试。

    /// <summary>
    /// Mocks an <see cref="EntityEntry"/>  for a given entity in the specified DbContext.
    /// </summary>
    /// <typeparam name="TContext">The type of the DbContext.</typeparam>
    /// <typeparam name="TEntity">The type of the entity.</typeparam>
    /// <param name="dbContextMock">The mock of the DbContext.</param>
    /// <param name="entity">The entity to mock the entry for.</param>
    /// <returns>A <see cref="Mock"> of the <see cref="EntityEntry"/> for the specified entity.</returns>
    /// <remarks>The method heavilly depends on "Internal EF Core API" and so can fail after EF upgrade. Use with extreme care.</remarks>
    [System.Diagnostics.CodeAnalysis.SuppressMessage("Usage", "EF1001:Internal EF Core API usage.", Justification = "<Pending>")]
    public static Mock<EntityEntry<TEntity>> MockEntityEntry<TContext, TEntity>(Mock<TContext> dbContextMock, TEntity entity)
    where TContext : DbContext
    where TEntity : class
    {
        var stateManagerMock = new Mock<IStateManager>();
        stateManagerMock
            .Setup(x => x.CreateEntityFinder(It.IsAny<IEntityType>()))
            .Returns(new Mock<IEntityFinder>().Object);
        stateManagerMock
            .Setup(x => x.ValueGenerationManager)
            .Returns(new Mock<IValueGenerationManager>().Object);
        stateManagerMock
            .Setup(x => x.InternalEntityEntryNotifier)
            .Returns(new Mock<IInternalEntityEntryNotifier>().Object);

        var entityTypeMock = new Mock<IRuntimeEntityType>();
        var keyMock = new Mock<IKey>();
        keyMock
            .Setup(x => x.Properties)
            .Returns([]);
        entityTypeMock
            .Setup(x => x.FindPrimaryKey())
            .Returns(keyMock.Object);
        entityTypeMock
            .Setup(e => e.EmptyShadowValuesFactory)
            .Returns(() => new Mock<ISnapshot>().Object);

        var internalEntityEntry = new InternalEntityEntry(stateManagerMock.Object, entityTypeMock.Object, entity);

        var entityEntryMock = new Mock<EntityEntry<TEntity>>(internalEntityEntry);
        dbContextMock
            .Setup(c => c.Entry(It.IsAny<TEntity>()))
            .Returns(() => entityEntryMock.Object);

        return entityEntryMock;
    }

使用此方法的结果，您可以轻松地为

ReloadAsync

创建所需的模拟：

 entityEntryMock.Setup(e => e.ReloadAsync(default)).Returns(Task.CompletedTask);