In April 2016 France joined many other countries (like Israel, India, Russia and the United States) and staged very realistic counterterrorism response exercises in a major city (in this case Paris.) Other countries (especially Israel, India, Russia and the United States) have learned that this is the only way to avoid unforeseen (and often fatal) problems when there is a major terror attack in a large urban area. It is common for the various available police and military emergency response organizations to not have a detailed response plan, especially a plan on how to work together. There is also a need for how to deploy unarmed medical and firefighting personnel.
Creating a plan that only exists on paper is often, actually almost always, found to have some serious flaws when put to the test during an actual attack. Local governments don’t like the realistic training exercises because they are expensive, disruptive (even when held in the middle of the night) and often create bad publicity for the local government. After a major terrorist attack in a city these attitudes change, which is why Israel, India, Russia, the United States, many other countries and now France have begun doing more of this. In mid-April Paris was the scene of several counter-terror and emergency organizations using realistic (with commandos playing the part of the terrorists) situations to see what aspects of the emergency plans still needed work.