VS MSTest runner locks System.Data.SQLite.dll when running in memory tests

Question

I'm using Fluent NHibernate to run in-memory database tests (MS Test) using SQLite 1.0.66.0:

[TestClass]
public abstract class InMemoryDatabaseTest
{
    private NHibernate.Cfg.Configuration configuration;
    private ISessionFactory sessionFactory;

    [TestInitialize]
    public void Initialize()
    {
        // All "CreateConfiguration" does is load FNh mappings.
        this.configuration = new NhConfigurationBuilder()
            .CreateConfiguration()
            .Database(() => SQLiteConfiguration.Standard.InMemory())
            .BuildConfiguration();

        this.sessionFactory = this.configuration.BuildSessionFactory();
    }

    [TestCleanup]
    public void Cleanup()
    {
        new SchemaExport(this.configuration).Drop(false, true);
        sessionFactory.Dispose();
    }

    protected ISession CreateSession()
    {
        var session = this.sessionFactory.OpenSession();

        // Re-create the database every time a new session is created.
        new SchemaExport(this.configuration)
            .Execute(script: false, export: true, justDrop: false, connection: session.Connection, exportOutput: null);

        session.BeginTransaction();
        return session;
    }
}

And then using this as an example:

[TestClass]
public class MessagesControllerTests : InMemoryDatabaseTest
{
    [TestMethod]
    public void SQLite_should_have_all_handles_released()
    {
        using (var session = this.CreateSession())
        {
            // Don't even need to do anything.
        }
    }
}

After running this test, I try to Clean the whole solution. The results are as follows:

When running this test (CTRL + R, CTRL + T), the clean is able to succeed as expected.
When debugging this test in (CTRL + R, T), the clean fails with the error: C:\Windows\Microsoft.NET\Framework\v4.0.30319\Microsoft.Common.targets(3607,9): warning MSB3061: Unable to delete file "PathToProject\bin\Debug\System.Data.SQLite.DLL". Access to the path 'PathToProject\bin\Debug\System.Data.SQLite.DLL' is denied.

My first thought was ok, delete the DLL. When I try to, I'm prompted that QTAgent32.exe is currently using the DLL. I used Process Explorer to verify this. For some reason the ms test runner is keeping a handle on the DLL. I've tried modifying the Cleanup metehod with some suggestions from another question, but it still didn't work:

[TestCleanup]
public void Cleanup()
{
    new SchemaExport(this.configuration).Drop(false, true);
    sessionFactory.Close();
    sessionFactory.Dispose();
    SQLiteConnection.ClearAllPools();
    GC.Collect();
}

I've been able to reproduce this on 3 different machines. Any know method to solve this issue would be greatly appreciated.

Update: I've cleaned up some linguistic confusion. The actual solution configuration can be in Debug/Relase. However, running the tests versus debugging the tests causes the difference in error messages.

Well, just to make sure the database is completely destroyed. — TheCloudlessSky, Jun 04 '11 at 10:00
That's strange that the path in the error message is bin\Debug even though you build in Release mode — Patrick McDonald, Jun 22 '11 at 23:22
@Patrick - Sorry, I meant *running* the tests versus *debugging* the tests. In both Release/Debug build configurations, the clean will fail after debugging the tests. — TheCloudlessSky, Jun 25 '11 at 18:10
Does calling GC.Collect twice work? (Unlikely but worth a try) http://stackoverflow.com/questions/3829928/under-what-circumstances-we-need-to-call-gc-collect-twice — Patrick McDonald, Jun 25 '11 at 20:53
I am having the same problem. QTAgent32 is holding on to SQLite.DLL and I am _not_ using NHibernate. — default.kramer, Apr 12 '12 at 20:06

score 0 · Answer 1 · answered Jun 22 '11 at 23:20

I was continually having a similar problem (SQLite.dll being locked by the Visual Studio test runner, although in Debug mode mostly and using MbUnit tests) and found that using TestDriven.net to run my tests solved the problem for me. I never looked any further into the MSTest runner after this, sorry.

VS MSTest runner locks System.Data.SQLite.dll when running in memory tests

1 Answers1