Mock DbContext with FakeDbSets

Question

I want to create a mocked DbContext using faked DbSets. So I've created a class called FakeDbSet<T> which implements IDbSet<T>.

Now I've created a FakeDbContext which has those faked DbSet<T>s in it. I've bound DbContext to FakeDbContext with Ninject like this:

Kernel.Bind<DbContext>().To<FakeDbContext>();

When I call my WebAPI project I'll get an SqlException that I don't have the permission to create the database.

This is my FakeDbContext:

public class FakeDbContext : DbContext
{
    public virtual IDbSet<User> Users => new UserDbSet();
}

(Note: UserDbSet just fills the HashSet<User> with default data.)

How do I set my FakeDbContext to not create/interact with a real database? If I remove the : DbContext from the FakeDbContext Ninject says that it must be convertible to DbContext.

Have you thougth about a framework like Moq? aikmeng.com/post/62817541825/… — ste-fu
– ste-fu, Commented Oct 2, 2015 at 15:44

qujck · Accepted Answer · 2015-10-02 15:43:12Z

2

Try disabling database initialisation

public class FakeDbContext : DbContext
{
    static FakeDbContext()
    {
        Database.SetInitializer<FakeDbContext>(null);
    }

    public FakeDbContext() { }

    public virtual IDbSet<User> Users => new UserDbSet();
}

This test works for me:

[Fact]
public void Test1()
{
    var kernel = new StandardKernel();
    kernel.Bind<RealContext>().To<FakeDbContext>();

    var result = kernel.Get<Wrapper>();

    var user = result.context.Users.Add(new User());
    Assert.NotNull(user);
}

public class Wrapper
{
    public readonly RealContext context;

    public Wrapper(RealContext context)
    {
        this.context = context;
    }
}

public class RealContext : DbContext
{
    public virtual IDbSet<User> Users => new UserDbSet();
}

public class FakeDbContext : RealContext
{
    static FakeDbContext()
    {
        Database.SetInitializer<FakeDbContext>(null);
    }

    public override IDbSet<User> Users => new UserDbSet();
}

// .....

edited Oct 2, 2015 at 15:43

answered Oct 2, 2015 at 14:45

qujck

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8 Comments

Stefan Schmid Over a year ago

Thanks this worked for me, but now I'm getting an error saying The underlying provider failed on Open.. How do I disable all interaction with real tables and databases?

qujck Over a year ago

Does an empty constructor help?

Stefan Schmid Over a year ago

Unfortunately not. It's stil trying to connect to the database on System.Data.Entity.Core.EntityClient.EntityConnection.Open().

Stefan Schmid Over a year ago

It's still trying to connect to that database. (I left the connectionString empty) Our problem is that we don't have a DB yet so we have to work with mocked data. How do I fix this?

Stefan Schmid Over a year ago

It's done by Ninject, I'm just injecting a DbContext into my services. In my question there's the line with the binding.

|

Stefan Schmid · Accepted Answer · 2015-10-05 07:14:18Z

0

I've finally fixed ith with qujck's help.

The reason why I was getting an exception because my DbContext tried to connect to the database was, that I was using DbContext.Set<T> which was accessing the database.

Overriding the Set<T> method fixed the problem.

answered Oct 5, 2015 at 7:14

Stefan Schmid

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