If you use assertEqual to compare two integers you get a message like

AssertionError: False is not true : Scalars failed to compare as equal! Comparing -6 and 0 gives a difference of 6, but the allowed difference with rtol=0 and atol=0 is only 0!

The stuff about rtol and atol is is needlessly obscure and obscures the fact that, e.g., the integers in question are exit codes, for example. One easy fix is to suppress rtol/atol sentence if those are exactly zero; I'd also suggest we shouldn't report "difference" for integer comparison.