Se trata de una entrada del blog About translation, de la asignatura Foundations of Translation del Univerity College de la Universidad de Denver.
Ahí va la información sobre el dilema de las pruebas de traducción para las agencias:
Often when we contact a translation company (and sometimes when a translation company contacts us), we are asked to do a translation test, or sample translation, as a preliminary to possible collaboration with them.
Many translators object to doing translation tests for free, on various grounds, from the fact that other professionals do not do free tests (which is not exactly true, as many lawyers and other professionals do provide free consultations, after which you can decide whether to retain them or not), to the fact that translation tests are allegedly used by unscrupulous agencies to stitch together the translation of an entire book done for free (which I have always thought a translator's urban legend, as this is something people always hear but never actually see first hand, and also because any agency that would attempt a stunt like that would soon be out of business, as the resulting quality of such a patchwork would certainly be abysmal).
Another objection is that translation tests mean little, and that translation companies should rely instead on the work experience, education, or other indicators of a translator's worth, which is a valid objection, but would not help one gain work from an agency who has decided to use translation tests in their screening process: normally, if you don't do the test, you also don't work for them.
In my opinion, the best objection to doing free translation tests is that one has no time for that: if you already have enough work, doing a translation test for free is probably not the best investment of your time.
If one decides to do the translation tests, there are several things to consider:
The test should be of an acceptable length (normally no more than 500 words or so).
Read carefully, and follow any instructions given together with the test: when I worked as a manager in the translation department of a major business software company, we used translation tests as a part of our screening process. We never asked to translate more than 250 to 350 words, but we normally sent out tests in which the words to translated were clearly marked within longer texts. Failure to follow the instructions (by, for example translating more than we had asked) was a serious mark against our candidates, since it was indicative that these translators would not be good at following instructions in a real work environment, either.
If you accept to do the test, do your best, and treat it as a real work assignment: put your best foot forward.
Do not leave alternate translations: you would not do that in a real work assignment, and you should not do in a test (any alternate translations left in a test would normally be marked as an error).
Do not add translator's notes, unless specifically requested to do so in the instructions: I've seen many apparently acceptable tests fail because the translation notes made clear that the translator had not, in fact, understood the meaning of some sentence or term.
Do not have someone else translate the test for you: I've seen it done, and more often than not cheats are quickly found out, if not during the test evaluation, eventually with the first work assignment.
Finally...
Do not use Babelfish to do the test (happened: we once received a test which looked really terrible. We began to joke that Babelfish probably would not do it worse, so we run the test through Babelfish, just to see how much worse a free MT program would do it... turned out it did it exactly the same, as the would be translator had used it to do the test).