An online testing system developed for entry-skills testing of first-year university students in algebra and calculus is described. The system combines the open-source computer algebra system "Maxima" with computer scripts to parse student answers, which are entered using standard mathematical notation and conventions. The answers can involve structures such as: lists, variable-precision-floating-point numbers, integers and algebra. This flexibility allows more sophisticated testing designs than the multiple choice, or exact match, paradigms common in other systems, and the implementation is entirely vendor neutral. Experience using the system and ideas for further development are discussed.