How to set up LocalDb for unit tests in Visual Studio 2012 and Entity Framework 5

We have a Visual Studio 2012 ASP.NET MVC project using Entity Framework 5.

There are some unit tests that depend on a database. Setting up the app.config file in the test project to use a central SQL Server database works fine.

However, it would be much nicer to use a LocalDb, so that each developer has his/her own database when running the tests. Especially since we would like to have the tests set up to DropCreateDatabaseAlways when running.

However, I can't get the setup to work. If I try this in app.config:

<add name="TestDb" 
   connectionString="Data Source=(LocalDb)\v11.0;Initial Catalog=unittestdb;
     Integrated Security=SSPI;AttachDBFilename=|DataDirectory|\unittestdb.mdf"
   providerName="System.Data.SqlClient" />

I get:

System.Data.SqlClient.SqlException: A file activation error occurred. The physical file name '\unittestdb.mdf' may be incorrect. Diagnose and correct additional errors, and retry the operation. CREATE DATABASE failed. Some file names listed could not be created. Check related errors.

It sounds like it wants the mdf file to exist already, which seems strange since it is trying to create the database. Creating a mdf file manually does not change the error message.

Try:

AppDomain.CurrentDomain.SetData(
  "DataDirectory", Path.Combine(AppDomain.CurrentDomain.BaseDirectory, ""));

This will Create Db File on /bin/Debug/yourdbname.mdf

I would use:

// Declare this property - this is set by MSTest
public TestContext TestContext { get; set; }

// In test initialization - note the signature should be exactly this
// A static void method with one argument of type TestContext 
[ClassInitialize]
public static void SetUp(TestContext context)
{
   AppDomain.CurrentDomain.SetData("DataDirectory", Path.Combine(context.TestDeploymentDir, string.Empty));
}

You could get problems using AppDomain.CurrentDomain.BaseDirectory, instead use: context.TestDeploymentDir

Keep in mind that for a test project:

AttachDBFilename=|DataDirectory|

means it will look in your output /bin/debug folder for a unit test as opposed to the App_Data folder in your web/production/whatever app.

You need to do two things 1. Move the database file OUT OF your App_Data folder to your root of your test app. 2. Highlight your database so you get your properties window in Visual Studio. Set the build action to "Content" so it will get copied to your output folder when you run the project.

Voila.

I suggest to use this code (based on the answer of Jupaol):

[ClassInitialize]
public static void SetUp(TestContext context)
{
    AppDomain.CurrentDomain.SetData(
        "DataDirectory", 
        context.TestDeploymentDir);
}

Usually this will create your database inside TestResults\<test run>\Out\ folder of your solution.