I'd like to believe that DNA testing, in the sense of determining the mix of your ancestry, is based on something scientific. It's not. It just isn't. It's more related to a statistical analysis of the similarities of test results, factoring in the likelihood of more intermediate generations connecting any two results by guessing at the possible variations, then logging the geographic locations of the participants. Thus, if the only people on a particular Greek island who have done a DNA test are people from England who've moved there for tax reasons, you could find yourself with Greek ancestry even they didn't know they had.
I have tried to defend the process. A work colleague from Brazil (with a Portuguese mother) wondered about her Irish ancestry, & I flubbed on about how Northern Spain & Portugal have old cultural links to the Celtic nations, so it's possible.
My cousin's daughter had a test done & was told she's 60% Scottish. That would only make sense if her father (who I don't know) was 100% Scottish (which I know he isn't), because she's got less than 10% from her mother's side.
It could be suggested that the above is based on personal opinion, & that's all well & good.
DNA tests are still bunkum.
To prove a point, I read somewhere that a particularly well known conservative red-haired Australian politician had taken a DNA test & been told she was 59% Northern European, 39% Eastern Mediterranean, & 9% Middle Eastern. That's a big number. One of her Great-grandparents must have been an Arab. No-one mentioned that in the article. My own Arab ancestry is so diluted that people laugh at me when I mention it, so I won't.
I'll also leave aside that politician's bland acceptance that one of her Great-grandparents had inexplicably been an Arab - & another 3 were Greek (or Turkish). She trusted 'the science' in the same way she'd been trusting her advisers for decades, I suppose.
Bunkum.
It just so happens that the lady in question has a well-known enough ancestry that it's on the web, & I've just trawled through 7 generations of her forebears, & I've discovered that she's about 25% Irish, 20% Cornish, & most of the rest is from Southern England. It's one of the least-travelled genealogies I've seen in a while.
Admittedly, one of her Great-grandparents is a bit of a mystery to me, having been born in London, where his father is listed at his wedding (in Brisbane), but not his mother. Maybe she was an Arab. More likely she was a common Londoner with a name like Mary. Her Irish ancestry becomes a little patchy prior to 1800, but that's what happens when records get destroyed.
Her ancestry includes no grand ambassadors to foreign lands, soldiers who brought back native wives, or adventurers who rambled the colonies seeking fame & fortune.
Not one.
Her paper trail of ancestry explains why she has red hair. No question. I'm unsure if the DNA test mentioned that.
By all means, spend your shekels on the test, just for fun, but don't expect science. It's a commercial contract you're entering into, & it probably means you've sold your own DNA by buying into the idea of 'finding something out' about yourself. Don't expect to be told you're the last Plantagenet (which is the Earl of Loudon, from memory) , or descended from Cleopatra's hand-maid. Expect nothing, & you'll be happy. Anything else might upset you.
One of your great-grandparents may have been an Arab, & now you have to work out which one.