If you spend lots of time on google earth studying the two bases SW of Teheran, and have some proficiency on imagesat analysis, you'll see that all the few "cavities" and other posssible test sites are far in between one another, like one kilometer, and it all looks quite primitive, and with only one spot for thrust tests. Furthermore, those so called 52 square KM pictures are nowhere to be seen since the explosion. So In reality, one missile exploded and the people standing close by just heated up. That's all, and it happens to everyone, once in a while.US, France, etc; but people stay further away, just in case...
U.S. weighs sanctioning Russia as well as China in cyber attacks (Reuters)
from the article: Top Iran general: Blast disrupted anti-Israel weapons program