Akinyemi, I find Google does that. I discover plagiarism frequently by putting the beginning of a text in it, or if you find it necessary put in at every sub-heading. Google picks up resonances and notifies you. I use it all the time and I find it efficient-as good as ones that cost.
I have just tried out the link you posted here and I want to share that the test works and is good. One snag is that one cannot put in more that 1,000 words at a time, but for checking one's papers, that is a minor inconvenience.
Thanking you so much - warm regards Tina
I repeat your link here https://smallseotools.com/