Authoritative Name Server Question

[Ultrajones]

I thought I read somewhere that an NS entry must have an associated address
record (not be an alias to some other name).

Is this a valid NS entry for testdomain.com?

testdomain.com.      IN    NS    ns1.somedomain.com.
Where ns1.somedomain.com. is an alias to ns.somedomain.com?

Thank you in advance for your reply.

Regards,
Ultrajones