You should change name of method from fixSize() to something meaningful, size should be fixed it means decrease or increase? Better to name this method as increaseSize()

Instead of making these static methods called on some array you pass in, how about making the class work like ArrayList, ie you create an object of that type and apply methods(like add/remove, size, get) that treat it as a List with unlimited( on a machine with inifinte memory and computation time ) size, but size() still returns the correct number of elements in that list.

Basically, a kata to make an implementation of ArrayList, hell, even add generics.

That's what I actually thought this kata was when I read the description.

Too vague. Solved by guesswork.

The instructions are too vague.

The big problem is that I don't understand the meaning of this problem!

Description of task is so crazy. I've not understood it.

ExtendArray.getLength doesn't get tested at all. However, neither ExtendArray.getLength nor ExtendArray.get actually contribute anything to the kata.

You're creating instances just to test static methods:

ExtendArray myExtendedArray = new ExtendArray();
assertEquals(myExtendedArray.get(changedArray, randomIndex), myExtendedArray.get(myArray, randomIndex));

That's quite strange. Instead, use the class method:

assertEquals(ExtendArray.get(changedArray, randomIndex), ExtendArray.get(myArray, randomIndex));

You don't actually tell what ExtendArray.fixSize should do. The name suggests that it should fix a broken size, but your code suggests that it should enlarge the array.

i think u need to rework this kata..
Task should be more interesting if it wont be like making size of array smthn bigger... It's nice to change the size dynamicly without collections and so on..
for exmple realize methods add() and delete() and if there's no free space for new element it should make array twice bigger and if it became smaller that 1/4 make the size twice smaller or something like this...