The Haskell Unfolder Episode 21: testing without a reference

The best case scenario when testing a piece of software is when we have a reference implementation to compare against. Often however such a reference is not available, begging the question how to test a function if we cannot verify what that function computes exactly. In this episode we will consider how to define properties to verify the implementation of Dijkstra’s shortest path algorithm we discussed in Episode 20; you may wish to watch that episode first, but it’s not required: we will mostly treat the algorithm as a black box for the sake of testing it.