A genetic test that decodes 100% of your DNA is called Whole Genome Sequencing. It includes sequencing all genes (coding regions), regulatory genomic regions, the Y chromosome (for males), and mitochondrial DNA. In contrast, other types of genetic tests examine less than 0.02% of your genome (e.g. tests from DNA companies such as AncestryDNA, 23andMe, MyHeritage DNA, and Living DNA).
It is the best DNA test for health and disease risk. You can learn more about Whole Genome Sequencing (and genetics and genomics in general) on the websites of the Centers for Disease Control and Prevention and the National Institutes of Health.