Depending on the university you attend, usually if you fail a class, you retake it. But failing one test worth 15% won't mean much. However, if you fail another exam then usually they take you in for assessment and see what went wrong and whether you should continue your studies with a retake OR expulsion from the course all together. This is what I was told though from a cousin who is a professor at university. But I am pretty sure this system only exists in the elite unis like usyd, unsw, unimelb, etc. But every other uni I think it is if you fail 3 exams. You should talk to your professor/lecturer and see what went wrong and seem like you actually care about you failing the test. Just keep trying for the future exams.
Good luck and hope all goes well.