A member of the NASASpaceflight.com forum has posted a large set of photos taken during Chang'E 3 thermal vacuum testing. They are all watermarked "China Space News" which is, as near as I can tell, a Chinese magazine -- I am hoping that the gigantic watermarks make it okay for me to post them. I'm posting them here in the spirit of asking forgiveness rather than permission, because I haven't been able to figure out a way to ask for permission. (EDIT: Here's where the photos were originally posted online.)
Thermal vacuum testing is one of the last major testing programs that a spacecraft has to endure before it is cleared for launch. It is a test that must be performed on the actual spacecraft that is headed for space -- not on an engineering model -- and it has to be done with the spacecraft essentially completely assembled. The whole ship is placed inside a testing chamber, and the chamber sealed and pumped down to as close to vacuum as is achievable. Then the chamber is run through temperature cycles to simulate the extreme heating and cooling that's experienced by a spacecraft exposed to alternating Sun and darkness in space.
Before I show you the photos, permit me an editorial comment: Oh my God, this thing is huge. In fact, it looks so huge that it makes me wonder whether it could serve as the base for a lander containing human astronauts. The rover is the rectangular box on top of the octagonal lander.
Here is a slightly closer view, in which you can see more detail on the rover, including its basket-like wheels.
A report on NASASpaceflight.com says that the current plan is to launch the lander and rover in December. China is actually building two complete spacecraft. Assuming that Chang'E 3 lands successfully, it is expected that China will do with the backup spacecraft what they did following the success of Chang'E 1: they'll launch the backup as a follow-on mission, called Chang'E 4.