Unit testing with EF Core and in memory database

It looks like you might want a class fixture.

When to use: when you want to create a single test context and share it among all the tests in the class, and have it cleaned up after all the tests in the class have finished.

Create a separate class to setup whatever data your tests will share, and to clean it up when the tests are finished running.

public class MovieSeedDataFixture : IDisposable
{
    public MovieDbContext MovieContext { get; private set; } = new MovieDbContext();

    public MovieSeedDataFixture()
    {
        MovieContext.Movies.Add(new Movie { Id = 1, Title = "Movie 1", YearOfRelease = 2018, Genre = "Action" });
        MovieContext.Movies.Add(new Movie { Id = 2, Title = "Movie 2", YearOfRelease = 2018, Genre = "Action" });
        MovieContext.Movies.Add(new Movie { Id = 3, Title = "Movie 3", YearOfRelease = 2019, Genre = "Action" });
        MovieContext.SaveChanges();
    }

    public void Dispose()
    {
        MovieContext.Dispose();
    }
}

Then use it in your tests by extending the IClassFixture<T> interface.

public class UnitTests : IClassFixture<MovieSeedDataFixture>
{
    MovieSeedDataFixture fixture;

    public UnitTests(MovieSeedDataFixture fixture)
    {
        this.fixture = fixture;
    }

    [Fact]
    public void TestOne()
    {
        // use fixture.MovieContext in your tests

    }
}

You can resolve the issue by appending the timestamp with the name of database name.

var myDatabaseName = "mydatabase_"+DateTime.Now.ToFileTimeUtc();

var options = new DbContextOptionsBuilder<BloggingContext>()
                .UseInMemoryDatabase(databaseName: myDatabaseName )
                .Options;

Only one database with given name is created in memory. (Documentation) Hence if you have same name this kind of exception may occur.

Similar discussion is there on this thread:

optionsBuilder.UseInMemoryDatabase("MyDatabase"); 

This creates/uses a database with the name “MyDatabase”. If UseInMemoryDatabase is called again with the same name, then the same in-memory database will be used, allowing it to be shared by multiple context instances.

And this github issue also suggests the same approach to add a unique string with database name Hope this helps.

Thanks, I did some changes in the fixture class and is working fine, even when I run both tests together.

Here is the change:

public class MovieSeedDataFixture : IDisposable
{
    public MovieDbContext MovieContext { get; private set; }

    public MovieSeedDataFixture()
    {
        var options = new DbContextOptionsBuilder<MovieDbContext>()
            .UseInMemoryDatabase("MovieListDatabase")
            .Options;

        MovieContext = new MovieDbContext(options);

        MovieContext.Movies.Add(new Movie { Id = 1, Title = "Movie 1", YearOfRelease = 2018, Genre = "Action" });
        MovieContext.Movies.Add(new Movie { Id = 2, Title = "Movie 2", YearOfRelease = 2018, Genre = "Action" });
        MovieContext.Movies.Add(new Movie { Id = 3, Title = "Movie 3", YearOfRelease = 2019, Genre = "Action" });
        MovieContext.SaveChanges();
    }

    public void Dispose()
    {
        MovieContext.Dispose();
    }
}