conftest.py defines an ApproxDict, which is a subclass of dict, whose equality method has been overridden such that, if a and b are dictionaries, then a == ApproxDict(b) will have the same truth value as a.items() >= b.items() (i.e. a is equal to ApproxDict(b) if a's key-value pairs are a superset of b's key-value pairs).

Since a.items() >= b.items() is a much clearer assertion than a == ApproxDict(b), let's replace usages of ApproxDict in our test suite with the more explicit assertion.