How To: Use EntityFramework Core In-Memory Database For Unit Testing

19 Mar 2018 in Unit Test on .Net , AAA Pattern , Database , Entity Framework , In Memory Database , SUT

In this post you will learn how to use entityframework in memory database.

You can download this article project on GitHub .

In this post, I’ll show how to use the in-memory feature of Entity Framework core to create unit tests involving the database. Let’s jump right in!

Create unit tests using a real DbContext is a pain because we have to mock the entire context to achieve this. Entity Framework core makes unit tests easier to write by providing us with an in-memory database provider. It creates an in-memory representation of our DbContext , for this reason, we don’t have to worry about mocking the database.

Setup your context

First, the database configuration must be done in the Startup.cs class, as it usually is in ASP.NET core projects. To illustrate:

public class Startup
    //...........
    //Other Stuff
    //...........
    // This method gets called by the runtime. Use this method to add services to the container.
    public void ConfigureServices(IServiceCollection services)
        services.AddDbContext<ToDoDbContext>(
            options =>
                options
                .UseSqlServer(Configuration.GetConnectionString("SimpleToDo")));
        //...........
        //Other Configurations
        //...........
    //...........
    //Other Stuff
    //...........

Next, the context should accept multiple database providers. We need a constructor which receives a DbContextOptions object:

public ToDoDbContext(DbContextOptions options) : base(options) { }

Finally, we can create the context with different configurations.

Create First Unit Test

We will add a new NuGet package to our unit test project. Open the package manager console and use the following command:

PM> Install-Package Microsoft.EntityFrameworkCore.InMemory

Now we can start to use the in-memory database feature.

Create a new unit test class for which functionality you want to test. In my case, it will be for the ToDoListRepository.cs .

public class ToDoListRepositoryTests
    [Fact]
    public void CreateToDoList_WithValidObject_NewListIdIsNotEqualsToZero()
        //Arrange
        var newToDoList = new List
            Name = "Unit Test"
        var sut = CreateSUT();
        //Act
        sut.CreateToDoList(newToDoList);
        //Assert
        Assert.True(newToDoList.ListId != 0);
    private ToDoListRepository CreateSUT()
        var dbOptions = new DbContextOptionsBuilder<ToDoDbContext>()
                            .UseInMemoryDatabase(databaseName: "ToDoDb")
                            .Options;