如何在单元测试中模拟或替换 Entity Framework 上下文？

Question

我想在我的一个项目中对业务逻辑组件进行单元测试。

BL:

public class CommunicationService
{
    IContext context;

    public CommunicationService()
    {
        var kernel = new StandardKernel(new NinjectConfig());
        context = kernel.Get<IContext>();
    }

    // This creates a file
    public void SomeMethodThatUsesIContext() { ... }
}

Ninject配置：

class NinjectConfig : NinjectModule
{
    public override void Load()
    {
        Bind<IContext>().To<CommunicationDbContext>();
    }
}

单元测试：

[TestMethod]
public void ScheduleTransportOrder_1()
{
    communicationService = new CommunicationService();
    communicationService.SomeMethodThatUsesIContext();
    Assert.IsTrue(...) // file should be created.
}

我在单元测试的项目中有另一个 Ninject 配置：

class FakeNinjectConfig : NinjectModule
{
    public override void Load()
    {
        Bind<IContext>().To<FakeDbContext>();
    }
}

并且我希望在单元测试中使用 IContext 的这个实现。但它仍然使用原来的 CommunicationDbContext 实现。我相信，当我在这里有另一个 ninject 配置时，它将被加载到内核中，但我想现在我误解了一些东西。你能帮我吗？

Answer 1

问题是您在 CommunicationService 构造函数中使用 NinjectConfig 而不是 FakeNinjectConfig 创建内核。

public class CommunicationService
{
    IContext context;

    public CommunicationService()
    {
        var kernel = new StandardKernel(new NinjectConfig());
        context = kernel.Get<IContext>();
    }

简单方法：

您可以创建一个新的构造函数来注入 NinjectModule 或 StandardKernel.

public CommunicationService (StandardKernel kernel) 
{
    context = kernel.Get<IContext>();
}

public CommunicationService(NinjectModule injectModule):this (new StandardKernel(injectModule))
{
    context = kernel.Get<IContext>();
}

public CommunicationService():this (new NinjectConfig())
{}

并且在测试中你可以用FakeNinjectConfig调用构造函数。

[TestMethod]
public void ScheduleTransportOrder_1()
{
    communicationService = new CommunicationService(new FakeNinjectConfig ());
    communicationService.SomeMethodThatUsesIContext();
    Assert.IsTrue(...) // file should be created.
}

或

[TestMethod]
public void ScheduleTransportOrder_1()
{
    communicationService = new CommunicationService(new StandardKernel(new FakeNinjectConfig ()));
    communicationService.SomeMethodThatUsesIContext();
    Assert.IsTrue(...) // file should be created.
}

正确方法：

但在我看来，您应该添加 IContext 作为依赖项并注入 IContext 解析 CommunicationService。

public class CommunicationService
{
    IContext context;

    public CommunicationService(IContext _context)
    {
       context = _context;
    }

然后，当您创建 CommunicationService 时，您应该使用内核的 Get 方法而不是 new 运算符。例如，而不是 communicationService = new CommunicationService() 你应该使用 communicationService = Kernel.Get<CommunicationService>();

[TestMethod]
public void ScheduleTransportOrder_1()
{
    var testKernel = new StandardKernel(new FakeNinjectConfig ());
    communicationService = testKernel.Get<CommunicationService>();
    communicationService.SomeMethodThatUsesIContext();
    Assert.IsTrue(...) // file should be created.
}

或者你可以直接注入IContext

[TestMethod]
public void ScheduleTransportOrder_1()
{
    communicationService = new CommunicationService(new FakeDbContext());
    communicationService.SomeMethodThatUsesIContext();
    Assert.IsTrue(...) // file should be created.
}

如何在单元测试中模拟或替换 Entity Framework 上下文？

How to mock or substitute Entity Framework context in unit test?

c#

unit-testing

ninject

mocking

entity-framework-6