RED - Peek() not implemented
Revert "RED - Peek() not implemented"

This reverts commit 91774f0d6803a537b8dc71d7e2490083039b0b7d.
RED - create test for getSize()
GREEN - getSize() implemented
REFACTOR - Added a @Before method that made code cleaner overall.
RED - added null check test for enqueue; failed.
GREEN - enqueue() now throws correct exception.
REFACTOR - added method description to getSize().