Sounds like a standard aptitude tests that companies have, rather than a full Visual Search Exercise (VSE) type test the OPC have (The ones requiring a mouse due to the type of test). If its a standard Verbal/Numerical reasoning test, you'll find it much easier with a computer, and apparently results have shown those who do these tests on a tablet or phone don't score as well due to concentration levels. So basically, you can probably get away with using a tablet, but you'll do better using a computer. I've also heard that doing these on a tablet or mobile device can cause strange things to happen such as screen freeze or not loading properly.
