Remove parameter check from each iteration

[ioanszabo]

• I removed the parameter check from each iteration.
• When second argument is not an array, the result is not build anymore, but function return first array which is the same.
• I've added two tests for cases when first or second argument is not array.
• I used 'Code reformat' in test file & somehow it rearranged, but tests are the same.

[rogervila]

Hi @ioanszabo
I already merged #4 but looks that this PR has lots of conflicts.

I want to thank you for the effort you put into working with this package.
I am closing this PR but feel free to reopen it if you want :)