Replace most toBeTruthy()/toBeFalsy() matchers with more specific ones in the unit-tests

[Snuffleupagus]

Generally speaking it seems like a good idea to have the unit-tests be explicit about their expected values, rather than accepting "arbitrary" truthy/falsy values.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.07%. Comparing base (99df11c) to head (963bd50).

Additional details and impacted files

@@           Coverage Diff           @@
##           master   #21739   +/-   ##
=======================================
  Coverage   90.07%   90.07%           
=======================================
  Files         264      264           
  Lines       67190    67190           
=======================================
+ Hits        60519    60521    +2     
+ Misses       6671     6669    -2     

Flag	Coverage Δ
unittest	58.25% <ø> (+<0.01%)	⬆️
unittestcli	56.61% <ø> (-0.03%)	⬇️

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[timvandermeij]

r=me, with the merge conflict fixed. This seems better indeed.