Stop interrupting the test suite at the first failure.

Stop interrupting the test suite at the first failure.

This behavior was useful when starting the implementation over
("take-2") where the whole test suite was failing. This made it easy
to focus on one test at a time and get each working.

More recently, we got the whole suite working, so we don't need this
feature anymore. And in the previous commit, we regressed a couple of
tests, so it's nice to be able to see all the failures with a single
run of the suite.