System to validate run time complexity requirements
Buffy is provably correct (no risk needed!) that it is impossible to do it with automated code analysis, as this is an attempt to figure out when a program will finish (i.e. the halting problem.)

You can get a very good guess, however, by using a few (very) differently sized input data sets, run the program on each one multiple times, and observe the results on a graph.  This is fairly trivial for a human, and takes very little time.  It may be less trivial for an automated statistical analysis, but I will defer to other who know more about such things to decide whether that is possible or not.