[enraged_camel]

It depends on whether they can show me some of their previous work, usually in the form of pictures from past projects. Serious vendors even invite prospective clients to their stores where they will have a "demo room" showcasing their work.

If they have neither, then it's absolutely fair to ask them to do a small audition project first. Otherwise how can you be sure they're competent?

Keep in mind this idea doesn't exist just in recruitment. It's basically recruitment's version of what's called a "proof of concept", which is proof that the party that is pitching/asserting something (i.e. their skill) can actually deliver.