I've seen this in aerospace in cases where testing the software against ground truth isn't possible for some reason[1], so you need to generate an alternative version of an algorithm as a sanity check.
[1] This is typically because the expected outputs are not easily known or specified in advance (e.g., interpolating a 3D wind cube to a higher resolution from lower resolution forecast data) and there isn't much if any experimental data, and collecting such data is expensive because it requires flying expensive aircraft around for long periods of time.
[1] This is typically because the expected outputs are not easily known or specified in advance (e.g., interpolating a 3D wind cube to a higher resolution from lower resolution forecast data) and there isn't much if any experimental data, and collecting such data is expensive because it requires flying expensive aircraft around for long periods of time.