Texas snakes that are black with one ring around its neck?

The snake you're describing is likely the Texas rat snake, also known as the Eastern rat snake (Pantherophis obsoletus). These snakes can exhibit various color patterns, including black bodies with a distinct darker or lighter-colored collar around the neck. They are non-venomous and are commonly found in Texas, often inhabiting forests, fields, and urban areas. Texas rat snakes are beneficial as they help control rodent populations.