[tptacek]

What is a warrant or subpoena but a demand by the state to surrender incriminating evidence?

You have a right not to testify against yourself. You do not have the right to conceal or destroy evidence!

[jsprogrammer]

The case you seem to be missing is when the testimony itself is evidence. Such a case seems to be protected by the fifth amendment.

How do you compel the production of evidentiary, self-incriminating testimony?

[tptacek]

See: any case where anyone has had voice mail entered into evidence against them --- which is something that has happened many times.