Geneology How accurate are they?

I have recently done a genealogy test, where I sent some swabs with saliva via mail, and I received results that were a bit surprising. Well, very surprising to me, as a matter of fact. While I know that most of my direct ancestors are from Jalisco and Zacatecas, I understand as well that some came from further like Spain and Italy, as I have heard. But when I saw that my genome was 12 percent Peruvian, well that was unexpected.
How accurate are these tests? I sent it to a reputable place I think. I Have been researching for a bit, and have been lucky to find ancestors up to the fifth generation, but so far all I get is "Yndio," Español", "Mestizo. None say Peruano. I also have North European, and some French and German, I expect that. I have no paper trail however.
Has anyone else found there research does not match their genome ?