Sklivvz is right in pointing out that Robinson does not claim that tests cause ADHD. Robinson questions the diagnosis in the first place. Since Robinson is the only source you've cited for your claim, this is the view that my response is aimed at.
Robinson frequently claims that ADHD is invented (in this TED talk, among other places). What we know for sure is that he doesn't know that for sure.
Robinson is making very bold claims outside of his own comfort zone (his PhD is in drama and education) and contradicts the consensus in medicine and psychology, where ADHD is treated as something very real. More than anything, his claims are emotional, anecdotal, and to me seem to reveal a gross missconception of what ADHD even is. Robinson will often say that children are different in several ways and that this should be encouraged. ADHD doesn't contradict that. ADHD is very specific. Although diagnosis is based on subjective judgement and there is no simple lithmus test to decide whether or not it is present in a given individual (much like most other psychogenic conditions, a line of argument I elaborated on in the question about addiction), it isn't enough to be fidgety and impatient, which are completely natural traits in children. In order to be diagnosed with ADHD, a child must meet several criteria on inattention and hyperactivity.
For Robinsons argument to have any bearing on the validity of ADHD at all, given how specific the diagnosis is, the argument should not simply be that children are different, but he'd have to argue that a subset of children are for some reason different in a very specific and uniform way. It is easy to understand that conformity of behaviour if you consider a psychogenic disorder (the mechanics of which are not at this point entirely understood) to be the common cause in all these children. If Robinson is to dismiss that explanation, he would have to provide another one, or at the very least a plausible reason for this dismissal. I have not seen Robinson put forth either, and as far as I can tell, his criticism is rooted in ignorance of the disorder at hand.
Given that ADHD does exist, is medication the proper way to deal with it? I'm not qualified to say. Are we currently over-diagnosing the condition? Possibly. A study I don't have access to apparently claims (according to Wikipedia) that diagnosis based on the DSM-IV criteria, which are used in the USA, will be 3-4 times more likely to positively diagnose ADHD, compared to the DCI-10, used in Europe. From this, we must deduce that either over- or under-diagnosis must reasonably be going on. I wouldn't debate Robinson if those were his focal points, but his broader claims that ADHD is invented are very controversial, and in stark contrast with the current consensus among those who are actually educated in the subject.