you can use a simulated Thymio to write programs, then test them on the real Thymio. The simulated Thymio is in a development version and has limited capacities compared to the real one, but it should help you.
How to simulate Thymio

We are starting a year-round robotics course with kids from local Italian and Slovene communities. This is a part of the social service of our students, who will teach local kids to program Thymio.
The problem is that we only bought one Thymio robot and we will have eight kids per group. We initially thought that there is a possibility that while some kids write their programmes, others can test their programmes with our Thymio. Pairs of kids would have Aseba installed on our college computers.
Unfortunatelly, it appeared that you can only start Aseba or VPL if you have wireless adapter connected to the computer.
Is there a solution to this problem (without buying more Thymios)?

Thank you,
Milos Busarcevic
United World College of the Adriatic
Duino, Italy
www.uwcad.it