In bottom-up testing, what is built to stand in for a higher-level module that does not exist yet, so that it calls the lower-level module under test, passes it test data and receives the results?

Answer: A. Driver

Bottom-up testing integrates modules starting from the lowest level, and because the calling higher-level module does not exist yet, a test program called a driver is written to call the module instead. Conversely, in top-down testing, which integrates from the top, a stub that simply returns fixed values is written to stand in for a lower-level module that does not exist yet. An in-circuit emulator is a debugging device connected to the board in place of the microcontroller, which can stop program execution and observe the internals on the real hardware.

• A. Correct. It is a test program that calls the module under test in place of the higher-level module.
• B. In top-down testing, this is the program that is called in place of a lower-level module that does not exist yet.
• C. This is a debugging device for stopping and observing a program on real hardware, not a substitute module for testing.