EF Core. DbContext uses wrong database

Question

I have declared my own DbContext:

public class DbContextMain: DbContext
{
   // some DbSets here 

   public DbContextMain(): base()
   {        
   }

   protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
   {        optionsBuilder.UseNpgsql("Host=myip;Username=postgres;Password=postgres;Database=test");
   }
}

Please note, that is being configured to use Database=test

But when I run the following code inside another console project:

static void Main(string[] args) {
    DbContextMain dbContextMain = new();
    dbContextMain.Database.Migrate();
}

I get strange exception:

Npgsql.PostgresException: "3D000: database "postgres" does not exist"

Please note, that database mentioned in exception is "postgres" while my database is "test" (and I double checked - method OnConfiguring is executed before Migrate call)

What I do wrong?