BDD or Behavior Driven Development is a development approach, but even if you don't utilize it, we think Cucumbe r (or a comparable tool) is useful since it "pushes" you to document your automated tests before implementing them. Cucumber is another traditional Selenium substitute, but there are some significant differences between the two systems. Cucumber is an automation tool for behavior-driven development(BDD), whereas Selenium is an automation tool for web apps.