comparers: Example Object and Side Effect Comparers#

Description#

Example two-argument functions to compare direct or indirect effects of two test descriptors (see P and R). These can be passed as value_comparer and sides_comparer to E.

Usage#

ignore_differences(x, y)

sides_similar(x, y)

Arguments#


`x`	prototype or part thereof
`y`	object under scrutiny or part thereof

Details#

Notable built-in (base R) comparers include identical (the strictest possible) and all.equal (can ignore, amongst others, round-off errors; note that it is an S3 generic).

ignore_differences is a dummy comparer that always returns TRUE. Hence, it does not discriminate between anything.

sides_similar is useful when comparing side effect lists. It defines the following semantics for the prototypical values:

non-existent, NULL, or FALSE – a side effect must not occur,
NA – ignore whatsoever,
TRUE – a side effect occurs, but the details are irrelevant (e.g., ‘some warning’ as opposed to "NaNs produced")
otherwise – a character vector with message(s) matched exactly.

You can define any comparers of your own liking: the possibilities are endless. For example:

a comparer for side effects based on regular expressions or wildcards (e.g., ".not converged.*"),
a comparer that tests whether all elements in a vector are equal to TRUE,
a comparer that verifies whether each element in a vector falls into a specified interval,
a comparer that ignores all the object attributes (possibly in combination with other comparers),

and so forth.

Value#

Each comparer should yield TRUE if the test condition is considered met or anything else otherwise. However, it is highly recommended that in the latter case, a single string with a short summary of the differences be returned, as in all.equal.

Author(s)#

Marek Gagolewski