Entity Framework Core / MongoDB: the entity type 'TestEntity' primary key property 'Id' must be mapped to element '_id'

I am writing a data access layer which is tested against multiple database implementations; some SQL (Postgres, Sqlite, SQL Server) and some document (MongoDB). In order to test different databases, my test fixtures include a test entity, entity configuration and DbContext.

For example:

TestEntity:

public sealed class TestEntity(Guid id, string text, int number, DateTime created)
{
    public TestEntity(string text, int number) : this(Guid.Empty, text, number, DateTime.UtcNow)
    {
    }

    public Guid Id { get; } = id;
    public string Text { get; } = text;
    public int Number { get; } = number;
    public DateTime Created { get; } = created;
    public Optional<DateTime> Updated { get; private init; } = Optional<DateTime>.None;
    public bool IsUpdated => Updated.HasValue;

    public TestEntity Update() => new(Id, Text, Number, Created) { Updated = DateTime.UtcNow };
    public override string ToString() => this.ToRecordString();
}

TestEntityTypeConfiguration:

public sealed class TestEntityTypeConfiguration : IEntityTypeConfiguration<TestEntity>
{
    public void Configure(EntityTypeBuilder<TestEntity> builder)
    {
        builder.HasKey(entity => entity.Id);
        builder.Property(entity => entity.Id).ValueGeneratedOnAdd();
        builder.Property(entity => entity.Text).IsRequired().HasMaxLength(32);
        builder.Property(entity => entity.Number).IsRequired();
        builder.Property(entity => entity.Created).IsRequired();
        builder.Property(entity => entity.Updated).HasConversion<OptionalValueConverter<DateTime>>();
        builder.Ignore(entity => entity.IsUpdated);
    }
}

TestDbContext:

public sealed class TestDbContext(DbContextOptions<TestDbContext> options) : DbContext(options)
{
    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        modelBuilder.ApplyConfiguration(new TestEntityTypeConfiguration());
    }
}

Note that the integration tests work for all SQL databases. Only MongoDB is failing with the following error:

The entity type ‘TestEntity’ primary key property ‘Id’ must be mapped to element ‘_id’

Given that I am testing against multiple database implementations, I cannot modify TestEntity, TestEntityTypeConfiguration, or TestDbContext without good reason, as I do not want the changes to impact integration tests currently working against SQL databases.

The MongoDB test class is as follows:

IsolatedRepositoryMongoDbIntegrationTests:

public sealed class IsolatedRepositoryMongoDbIntegrationTests(ITestOutputHelper output) : IsolatedRepositoryIntegrationTests(output)
{
    private readonly MongoDbContainer container = new MongoDbBuilder()
        .WithUsername("test_user")
        .WithPassword("test_password")
        .WithWaitStrategy(Wait.ForUnixContainer().UntilPortIsAvailable(27017))
        .Build();

    protected override void ConfigureServices(IServiceCollection services)
    {
        services.AddDbContext<TestDbContext>(ConfigureDatabase);
        services.AddSingleton<IIsolatedRepository<Guid, TestEntity>, TestIsolatedRepository>();
    }

    private void ConfigureDatabase(DbContextOptionsBuilder builder)
    {
        IMongoClient client = new MongoClient(container.GetConnectionString());
        builder.UseMongoDB(client, "test_db");
    }

    public override async Task InitializeAsync()
    {
        await container.StartAsync();
    }

    public override async Task DisposeAsync()
    {
        await container.StopAsync();
        await container.DisposeAsync();
    }
}

Note that IsolatedRepositoryMongoDbIntegrationTests inherits the actual test cases from IsolatedRepositoryIntegrationTests, therefore this class only needs to contain the configuration for MongoDB.

Have I missed some configuration somewhere, or is there some configuration I should add to IsolatedRepositoryMongoDbIntegrationTests in order to make the tests pass?

I have searched for the error but haven’t found any documentation relating directly to MongoDB and Entity Framework Core, so if you know of anything I should read, please let me know.