My formulation is "if it's not trivial, it's probably not good" when I implement the necessary functions for the "type class" (to take a haskellism) to work. If your `bind` implementation monad doesn't look like it could have been written by someone who just used the function types, it's probably not right. Thanks for the link to the mcbride-ism:

https://personal.cis.strath.ac.uk/conor.mcbride/PolyTest.pdf