Using Entity Framework Core 3.1 with UseInMemoryDatabase option in ServiceProvider ( Scoped lifetime )

Question

I have migrated a web application project from .NET Core 2.1 to 3.1 (also EF Core from 2.1.1 to 3.1.0).

After the migration, some unit tests are not working anymore, throwing duplicate keys db exception.

I simulated the problem and realize that EF core with option UseInMemoryDatabase is behaving differently in 3.1, it does not clean up the old data.

In the second test method, the People table already contains data added from the first test, which is not happening in 2.1

Does anyone know how can I make in-memory database to be scoped to each unit test?

Here is my testing code:

AppDbContext.cs

using Microsoft.EntityFrameworkCore;
using System;
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;
using System.Text;

namespace MyConsoleApp.Database
{
    public class AppDbContext: DbContext
    {
        protected AppDbContext(DbContextOptions options) : base(options) { }

        public AppDbContext(DbContextOptions<AppDbContext> options) : this((DbContextOptions)options)
        {
        }

        public virtual DbSet<Person> Person { get; set; }
    }

    public class Person
    {
        [Key]
        public int Id { get; set; }
        public string Name { get; set; }
    }
}

AppUnitTest.cs

using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.VisualStudio.TestTools.UnitTesting;
using MyConsoleApp.Database;
using System.Linq;

namespace MyConsoleAppTest
{
    [TestClass]
    public class AppUnitTest
    {
        public ServiceCollection Services { get; private set; }
        public ServiceProvider ServiceProvider { get; protected set; }

        [TestInitialize]
        public void Initialize()
        {
           Services = new ServiceCollection();

           Services.AddDbContext<AppDbContext>(opt => opt.UseInMemoryDatabase(databaseName: "InMemoryDb"), 
               ServiceLifetime.Scoped, 
               ServiceLifetime.Scoped);

            ServiceProvider = Services.BuildServiceProvider();
        }

        [TestMethod]
        public void TestMethod1()
        {
            using (var dbContext = ServiceProvider.GetService<AppDbContext>())
            {
                dbContext.Person.Add(new Person { Id = 0, Name = "test1" });
                dbContext.SaveChanges();
                Assert.IsTrue(dbContext.Person.Count() == 1);
            }
        }

        [TestMethod]
        public void TestMethod2()
        {
            using (var dbContext = ServiceProvider.GetService<AppDbContext>())
            {
                dbContext.Person.Add(new Person { Id = 0, Name = "test2" });
                dbContext.SaveChanges();
                Assert.IsTrue(dbContext.Person.Count() == 1);
            }
        }

        [TestCleanup]
        public virtual void Cleanup()
        {
            ServiceProvider.Dispose();
            ServiceProvider = null;
        }
    }
}

MyConsoleAppTest.csproj

<Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
    <TargetFramework>netcoreapp3.1</TargetFramework>
    <IsPackable>false</IsPackable>
  </PropertyGroup>

  <ItemGroup>
    <PackageReference Include="Microsoft.EntityFrameworkCore.InMemory" Version="3.1.0" />
    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="16.2.0" />
    <PackageReference Include="MSTest.TestAdapter" Version="2.0.0" />
    <PackageReference Include="MSTest.TestFramework" Version="2.0.0" />
    <PackageReference Include="coverlet.collector" Version="1.0.1" />
  </ItemGroup>

  <ItemGroup>
    <ProjectReference Include="..\MyConsoleApp\MyConsoleApp.csproj" />
  </ItemGroup>

</Project>

Answer 1

I made the following Extension method for my UnitTest:

public static class ServiceCollectionExtensions
{
    public static IServiceCollection AddInMemoryDbContext<TDbContext>(this IServiceCollection services) where TDbContext: DbContext
        => services.AddDbContext<TDbContext>(builder
            => builder.UseInMemoryDatabase(Guid.NewGuid().ToString())
                .ConfigureWarnings(w =>
                    {
                        w.Ignore(InMemoryEventId.TransactionIgnoredWarning);
                        w.Throw(RelationalEventId.QueryClientEvaluationWarning);
                    }
                ), ServiceLifetime.Transient);
}

The usage is very simple. Just add all of your DbContext to your IServiceCollection on UnitTest setup.

...

services
    .AddInMemoryDbContext<AppDbContext>()
    .AddInMemoryDbContext<FooDbContext>()
    .AddInMemoryDbContext<AnotherDbContext>();

...

You also need to install Microsoft.EntityFrameworkCore.InMemory (https://www.nuget.org/packages/Microsoft.EntityFrameworkCore.InMemory)

Answer 2

If you want to do in-memory database to be used for unit testing, you can use the nuget package that microsoft provides for it:

Install-Package Microsoft.EntityFrameworkCore.InMemory -Version 3.1.5

And also to configure that you can fake the DbContext and the repositories, for example:

namespace YourProject.Tests.UnitTests
{
    public class FakeDbContext : DbContext
    {
        public DbSet<Entity> Entities { get; set; }    

        protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        {
            optionsBuilder.UseInMemoryDatabase(databaseName: "FakePersonalSiteDbContext");
        }

        protected override void OnModelCreating(ModelBuilder modelBuilder)
        {
            base.OnModelCreating(modelBuilder);
            AddMappingOverrides(modelBuilder);
        }

        private void AddMappingOverrides(ModelBuilder modelBuilder)
        {
            modelBuilder.ApplyConfiguration(new SomeEntityMappingOverride());
        }
    }
}

And then u can use this FakeDbContext to inject to a FakeRepository in unit testing project:

namespace YourProject.Tests.UnitTests
{
    public class FakePersonalSiteRepository : IYourRepository
    {
        private FakeDbContext dbContext;

        public FakeRepository(FakeDbContext dbContext)
        {
            this.dbContext = dbContext;
        }

        // Your repository methods (Add, Delete, Get, ...)
    }
}

That way now you can use a in-memory database to your unit tests. For example:

namespace YourProject.Tests.UnitTests
{
    public class UnitTestBase
    {
        protected IYourRepositoryRepository Repository { get; set; }
        protected FakeDbContext FakeDbContext { get; set; }

        [SetUp]
        public void SetUp()
        {
            FakeDbContext = new FakeDbContext();
            FakeDbContext.Database.EnsureDeleted();
            Repository = new FakeRepository(FakeDbContext);
        }
    }
}

Answer 3

You can install the package via package console

Install-Package Microsoft.EntityFrameworkCore.InMemory -Version 3.1.5

https://www.nuget.org/packages/Microsoft.EntityFrameworkCore.InMemory

Answer 4

I would personally build a service-provider for each test so you'll make sure that there is no shared-state between tests that are being executed simultaneously. Something like this:

private IServiceProvider BuildServiceProvider()
{
    var services = new ServiceCollection();

    services.AddDbContext<AppDbContext>(opt => opt.UseInMemoryDatabase(databaseName: "InMemoryDb"), 
        ServiceLifetime.Scoped, 
        ServiceLifetime.Scoped);

    return services.BuildServiceProvider();
}

Then use this function to build the provider in each test

[TestMethod]
public void TestMethod1()
{
    using (var serviceProvider = BuildServiceProvider()) 
    {
        using (var dbContext = serviceProvider.GetService<AppDbContext>())
        {
            dbContext.Person.Add(new Person { Id = 0, Name = "test1" });
            dbContext.SaveChanges();
            Assert.IsTrue(dbContext.Person.Count() == 1);
        }
    }
}

This might cause the execution time to be a little bit higher than before but should definitely prevent your current problem from happening again.

Tip:

You could also use the c# 8 syntax using statements now since you are running on netcoreapp3.1

[TestMethod]
public void TestMethod1()
{
    using var serviceProvider = BuildServiceProvider();

    using var dbContext = ServiceProvider.GetService<AppDbContext>();

    dbContext.Person.Add(new Person { Id = 0, Name = "test1" });

    dbContext.SaveChanges();

    Assert.IsTrue(dbContext.Person.Count() == 1);
}

Answer 5

The solution for me was to change the database name with unique name.

Services.AddDbContext<AppDbContext>(opt => opt.UseInMemoryDatabase(databaseName: Guid.NewGuid().ToString()), ServiceLifetime.Scoped, ServiceLifetime.Scoped);

In this way there is a new database for each test method.

See the github issue: https://github.com/dotnet/efcore/issues/19541