Depending on use case, could use screen sharing software. That way, they can use the environment they're comfortable with, rather than some arbitrary text editor. That way you can truly see how effective they are at working, rather than testing how well they can figure out a new text editor.
Always hunt-and-seek in menus to get commands done, or using keyboard shortcuts? Aware of features of IDE or not? CLI skills? SO driven development? Docs? etc.