Add tests for IStructuralEquatable/Comparable throwing NullReferenceException

[hughbe]

Closes #13410
Closes #13429

/cc @stephentoub @jcouv

[jcouv]

@stephentoub My intuition is that changing the thrown exception from System.Tuple APIs is a breaking change. Is that correct?
If we do decide to make this change, we should flag or track this to make the same change to various mscorlibs that are not public (.Net desktop).

FYI @KevinRansom This PR proposes to change the exception thrown by both System.Tuple and ValueTuple.

[stephentoub]

My intuition is that changing the thrown exception from System.Tuple APIs is a breaking change. Is that correct?

Correct

This PR proposes to change the exception thrown by both System.Tuple and ValueTuple.

Has the PR been updated? It looks like it's only adding tests at this point, not changing any exception-throwing logic in implementation.

[jcouv]

Consider adding a [Fact] on this so it runs as its own test (no need to invoke it from method above). Same suggestion for similar methods.

[hughbe]

Currently this is not possible, as no classes inherit from TupleTestDriver, so the [Fact] test will never run.

If you see the meat of the Tuple tests below, we have to call each test manually

[hughbe]

Obvi, this should be cleaned up/fixed up, but for another PR

[jcouv]

My bad. I got confused by the comment saying this fixes linked issues. Thanks for the correction.

The tests LGTM, although I'd suggest tagging the new methods as their own [Fact]. Thanks
#Closed

[hughbe]

@jcouv my fault too - I just updated the description to say "closes" instead of "fixes"

[joperezr]

Tests LGTM

[jcouv]

@hughbe Thanks!