As there are no other ways in which the thunk may possibly be exited, it is unattainable for a testcase to develop a consequence that would not in good shape into the framework (except your testcase manages both to crash Guile or enter an infinite loop - in which situation you is not going to get any output). In "The Princess and the Pear", he admitted to getting a "geek" and went undercover for a circumstance at Imagicon, a fantasy convention.