How to seed test data using WebApplicationFactory?

I'm working on integration tests for .NET Core 3.1 Web API. I followed this article Painless Integration Testing with ASP.NET Core Web API. This is my CustomWebApplicationFactory:

public class CustomWebApplicationFactory<TStartup> : WebApplicationFactory<TStartup> where TStartup : class
{
    protected override void ConfigureWebHost(IWebHostBuilder builder)
    {
        builder.ConfigureServices(services =>
        {
            var descriptor = services.SingleOrDefault(d => d.ServiceType == typeof(DbContextOptions<TestDbContext>));
            if (descriptor != null)
            {
                services.Remove(descriptor);
            }

            services.AddDbContext<TestDbContext>(options =>
            {
                options.UseInMemoryDatabase("InMemoryTestDb");
            });

            var sp = services.BuildServiceProvider();

            using (var scope = sp.CreateScope())
            {
                var scopedServices = scope.ServiceProvider;
                var db = scopedServices.GetRequiredService<TestDbContext>();
                var logger = scopedServices.GetRequiredService<ILogger<CustomWebApplicationFactory<TStartup>>>();

                db.Database.EnsureCreated();

                try
                {
                    Console.WriteLine("Seeding...");

                    var players = Utilities.GetTestPlayers(); // Returns 3 test players
                    db.Players.RemoveRange(db.Players); // Clear the table
                    db.Players.AddRange(players); // Add 3 test players
                    db.SaveChanges();

                    Console.WriteLine($"Players seeded: { db.Players.Count() }");
                }
                catch (Exception ex)
                {
                    logger.LogError(ex, "An error occurred seeding the " + "database with test messages. Error: {Message}", ex.Message);
                }
            }
        });
    }
}

These are my tests: For each Controller I created tests in separate class. In the constructor of test class I create a Client. Like this for TestController (I have total 4 Controllers in the API):

public class BaseControllerTest : IClassFixture<CustomWebApplicationFactory<Startup>>
{
    protected HttpClient Client { get; }

    public BaseControllerTest(CustomWebApplicationFactory<Startup> factory)
    {
        Client = factory.CreateClient();
    }
}

public class TestControllerShould : BaseControllerTest
{
    public TestControllerShould(CustomWebApplicationFactory<Startup> factory)
        : base(factory)
    {
        Console.WriteLine("TestControllerShould");
    }

    [Fact]
    public async Task GetHelloWorld()
    {
        var request = new HttpRequestMessage(new HttpMethod("GET"), "/test/");
        var response = await Client.SendAsync(request);

        Assert.Equal(HttpStatusCode.OK, response.StatusCode);
        var content = await response.Content.ReadAsStringAsync();
        Assert.Equal("Hello World!", content);
        Assert.False(response.Headers.Contains("Server"), "Should not contain server header");
    }
} 

My problem is:

As you can see in the CustomWebApplicationFactory I'm logging while seeding, and this is the log I see:

Seeding...
Seeding...
Seeding...
Seeding...
Players seeded: 12
Players seeded: 12
Players seeded: 12
Players seeded: 12

I have total of 4 Controllers and I'm seeding only 3 players. Why Am I seeing 12? I don't understand. It looks like line db.Players.AddRange(players); is called 4 times (for each Controller test class) before any db.SaveChanges();. Then db.SaveChanges(); is called 4 times in a row. Why?

My question is: Why is that? and How to properly seed test data in integration tests?

(if not by answer, any reference to a nice article will be greatly appreciated)

Thank you