public string Values_Internal { get; set; }

[NotMapped]
public List<double> Values
{
	get
	{
		var values =
			Values_Internal
			.Split(';')
			.Select(val => double.Parse(val))
			.ToList();

		return values;
	}

	set
	{
		Values_Internal = string.Join(";", value);
	}
}

                    var t = db.Tests.First();
                    db.Tests.Remove(t);

                    db.SaveChanges();

public class Test
{
    public int TestId { get; set; }

    public virtual CommonSettings CommonSettings { get; set; }
}

public class CommonSettings
{
    [Key, ForeignKey("Test")]
    public int TestId { get; set; }
    public virtual Test Test { get; set; }
}

// Configure TestId as FK for CommonSettings
modelBuilder.Entity<Test>()
	.HasOptional(e => e.CommonSettings) // Mark CommonSettings is optional for Test
	.WithRequired(ad => ad.Test) // Create inverse relationship 
	.WillCascadeOnDelete(true);

public class Test
{
    public int TestId { get; set; }

    public virtual CommonSettings CommonSettings { get; set; }
}

public class CommonSettings
{
    [Key, ForeignKey("Test"), Required]
    public int TestId { get; set; }
    public virtual Test Test { get; set; }
}

public override void Up()
{
    DropForeignKey("dbo.CommonSettings", "TestId", "dbo.Test");
    AddForeignKey("dbo.CommonSettings", "TestId", "dbo.Test", "TestId");
}

public override void Down()
{
    DropForeignKey("dbo.CommonSettings", "TestId", "dbo.Test");
    AddForeignKey("dbo.CommonSettings", "TestId", "dbo.Test", "TestId", cascadeDelete: true);
}

[Key, ForeignKey("Test"), Required]