Faking with a Function Pointer
Let’s use our random minute generator for the randomized light schedule feature. The scheduler will have unpredictable results because of its unpredictable indirect input from RandomMinute_Get. When production code depends on something unpredictable, it’s time to substitute in a test double. We have a problem; the binding of the LightScheduler to RandomMinute_Get is done by the linker, as you can see by looking at the interface of RandomMinute:
| t0/include/HomeAutomation/RandomMinute.h | |
| | void RandomMinute_Create(int bound); |
| | int RandomMinute_Get(void); |
Before we refactor the interface to allow function pointer substitution, let’s design the test for the randomized schedule.
| t0/tests/HomeAutomation/LightSchedulerRandomizeTest.cpp ... |
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