I'm going to say I'm practicing with my "girlfriend"
Is that an actual girlfriend? What are you practicing?
Yes, it's for a test. Also I'm practicing kissing and sex like you said.
it is wrong to lie to people. You could make her uncomfortable if someone else mentions it to her and you will break up.
it's just a little white lie.
Who are you actually trying to impress, and what kind of test needs this kind of practice...? I think you need to just be honest on what you are doing, your girlfriend might not like that she is being used in a way. Respect going both ways is healthy in a relationship.