Just like with the first company, the code was fragile. Any change in the under-tested code would result in remote failures far from the source. Their strategy was to change as little as possible, and have code reviews with three other people on the team enforcing this conservatism. In addition, they developed local experts, who acted as guard dogs to fenced areas of code. These areas were unofficially owned by them, and the rest of the team stood back heeding their warning, and warping the product to avoid entry into these arenas.