I never, ever do unpaid tests.
Well. Maybe sometimes.
The problem, as I see it, is that there are unpaid tests and there are unpaid tests, and each of them has to be considered separately. When I first started off, I did lots of unpaid tests for various translation agencies, naively thinking that it was the best way to kick-start my career, but they yielded poor results. Most of the time, I never heard from them again, or if I did, I was informed that I was now in their "freelancers’ database" and would be contacted as soon as a suitable job cropped up. Which rarely did. But come to think of it, what do these tests prove? Nothing! If you’re a bad translator trying to con agencies, you could just pay a good colleague to do the test for you. On the other hand, I did gain an excellent client who I still invoice every single month five years later. However, this is the exception, not the rule. Now that I have the benefit of experience and that I’m not quite as desperate to gain new clients, I would never again take a random unpaid test for a translation agency.
However, recently I was contacted by a department of an English university to take on a large project (50,000 + words). They had found my website and thought I might be able to help them. Although my profile satisfied them, they wanted to check for themselves whether I was capable of producing a good translation of their important and lengthy document, and asked whether I’d translate a short sample of it for free. I said yes, for different reasons: first of all, the woman who contacted me was extremely professional in her approach, and I liked the tone and detail of her emails. Second, it is a large project, with a tight deadline, and I can understand that they want to make absolutely sure that there will be no quality issue. Although my qualifications and experience prove that I am a "serious" translator, the subject of that document is so specific that they weren’t necessarily enough to guarantee I was the best person for that particular job. Third, I really wanted to take on this job! Apart from the fac that December and January are normally quiet months, I was really interested in the subject matter and know that I’ll enjoy working on the translation.
They reviewed my test very quickly and came back to me with valuable comments on my translation, and now I can look forward to developing a good working relationship (hopefully!) with an interesting direct client.