should be || should_not be: that is the expectation:
Whether 'tis nobler in the parser to interpret
The outputs and side effects of outrageous duck typing,
Or to inherit against a sea of matchers
And by declaration extend them?  To fail: to raise;
No more; and by a raise to say we throw
The exception and the thousand natural returns
The code is heir to, 'tis a specification
Devoutly to be wished.  To fail: to raise;
To raise, perchance to rescue: ay, there's the rub,
For in that state of exception what tests may fail
When we have injected in this matcher code
Must give us pause: there's the RSpec
That makes calamity of such long backtraces;
For who would bear the Flogs and Heckles,
The oppressor's Reek, the proud man's Cucumber,
The pangs of despised Rcov, the spec_server's Drb,
The insolence of Autotest and the spurns
That patient merit of the occasional Rakes,
When he himself might his validation make
With a bare assertion?  .....

— Stephen Eley (and his muse)