The gson JsonParser is final and it's #parse(JsonReader json) does this:
json.setLenient(true); 

In my unit tests I validate the output of my json rest api and I would like to 
have a parser with strict parsing. Creating my own StrictJsonReader also is not 
possible unless I put it in the com.google.gson package.

Maybe you could add a setter or constructor param for lenient or strict parsing?