Added unit test for getPrefix method
Added unit tests for some Str methods (lower, upper, limit, length methods.)
test values changed
Fix validator docblock
Merge pull request #5815 from lucasmichot/4.2-validator-docblocks

[4.2] Validator : fix validator docblock
Merge pull request #5803 from adililhan/4.2

Added unit test for getPrefix method
Merge branch '4.2'