Set theorem counter to be Roman

Question

I wanted to make the counter for a theorem displayed as capital roman numerals (I, II, III), but none of these attempts worked

\newtheorem{test}[\Roman{counter}]{Theorem}
\newtheorem{test}[Roman]{Theorem}

Is there a way to do this?

Answer 1

Simply use:

\newtheorem{test}{Theorem}
\renewcommand\thetest{\Roman{test}}

Defining a new theorem environment test defines a new counter test. The optional argument, such as you used, says the ‘test’ environment shares the counter of another theorem-like environment.