[REFACTOR] Remote class tests

https://app.asana.com/0/12866594763058/13353435202410

We're deferring testing data connections, like api or db requests.
But still I decided to commit my commented code, to make it easier
in the future.
[REFACTOR] Conversion class test

https://app.asana.com/0/12866594763058/13353435202410
[REFACTOR] Uuid class tests

https://app.asana.com/0/12866594763058/13353435202410
[REFACTOR] Refactor isJson() to be static

https://app.asana.com/0/12866594763058/13455847179727
Merge branch 'refactor/utils-json' into refactor/php-unit-tests
[REFACTOR] Json class tests

https://app.asana.com/0/12866594763058/13353435202410