Q: When writing pure software often stubs are used to return values to emulate an external environment, moreso for a program that must interact externally. How do you simulate the effect of interaction before commiting to the actual external environment at the testing stage? ( bottom-up vs top-down approach).
A: Years ago I had to build an instrument to acquire data from chemical instruments. I used a large EPROM to store a simulated waveform and then fed it to a DAC with an R/C filter to simulate the signal. That gave me a "standard" to use for testing. As an alternate, I could have saved this data in memory and written a routine to obtain it form that memory instead of using an ADC to digitize the DAC's output. But, in those days, memory was expensive and processors couldn't address more than 64 Kbytes. Is that what you're getting at?
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