simple tests to cextend our coverage

**Is your feature request related to a problem? Please describe.**
Sd -> Elnur -> tests as similar function, that we have it at fetch. Just have a separated file for it for a first time. If it(when) it will work, let's back to discussion and maybe upgrade tests then(tests that we have).

Stage1: file that have "isset" test: with checking if it works well + info
Stage2: replace that function at our load of files at different files.
Stage3: have one file, that have all of that calls for all files + remove if from separated files.

Question: Does all files inside one folder (new files) or how we are located them now?
Can you, Elnur explain it at Readme file, with Vadim help for me?

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