java.util。MissingResourceException:无法找到基名javax.servlet的bundle。LocalStrings、区域es_ES

I am trying to perform some jUnit test in one of my servlets but whenever I try to run it I obtain a ExceptionInInitializerError. I've read that this error is due to an exception, occurred during evaluation of a static initializer or the initializer for a static variable. The thing is that even though I tried to fix it I can. That's why I am writing here: my servlet code is the following:I am trying to perform some jUnit test in one o