Stubs:
- What are they?: Stubs are like placeholders or stand-ins for modules or components that aren’t ready yet. They mimic the behavior of lower-level modules that higher-level modules depend on.
- When are they used?: They’re typically used in a testing approach called top-down integration testing. This means you’re starting with the main parts of your software and simulating the smaller pieces that haven’t been built yet.
- How do they work?: Let’s say you’re testing a program that sends messages. If the part that actually sends messages hasn’t been created yet, you’d use a stub. The stub would pretend to send messages and return some predetermined response, like “message sent successfully” or “error sending message.”
- Purpose: Stubs help you keep testing on track even when some parts of your software aren’t fully ready. They make it possible to test higher-level functionality without waiting for all the lower-level details to be finished.
Drivers:
- What are they?: Drivers are like helpers that simulate the behavior of higher-level modules when testing lower-level ones. They provide inputs and mimic the behavior of the parts that haven’t been built yet.
- When are they used?: They’re often used in a testing approach called bottom-up integration testing. This means you’re starting with the smaller, foundational parts of your software and simulating the bigger pieces that depend on them.
- How do they work?: Let’s say you’re building a game and working on the part that handles player movement. If the part that controls the game levels isn’t ready yet, you’d use a driver. The driver would simulate different game levels and send inputs to the player movement part to see how it responds.
- Purpose: Drivers help you test the foundational parts of your software even if the higher-level features aren’t fully developed. They ensure that each piece you build works correctly before you put everything together.
So, while stubs and drivers both help you test software that’s still in progress, they do it in slightly different ways depending on whether you’re focusing on the top-down or bottom-up approach.