How do you decide if a force is conservative if you don't know if it produces heat?

The non-conservative forces familiar to us-- friction, drag, etc. do often result in heat lost to the environment. However the definition of a non-conservative force does not depend on nature of energy loss. A conservative force $\vec{F}(\vec{r})$ is defined as one for which work done over a path from one position to another does not depend on the path, but rather depends only on the endpoints.