All the setup/teardown/pre/post/conditions template methods
now are required to return void. This was warned with phpunit 7
and now is enforced.
At the same time, fix a few wrong function names,
provider data and param types, return statements...
There are various places where it's not guaranteed that the
variable being used is array, and instead, can be null, bool, int...
We need to check that because php74 warns about it.
Where possible we have used the coalesce operator as
replacement for isset() ternary operations.
Eloy Lafuente (stronk7)