time for a quick string calculator kata
first failing test case
pass
fails for identity
coerce to number
numbers separated by ,
passing test
failing to handle numbers with newlines
brute force that test to pass
failing test case for custom delimiters
make the test pass
extract helpers
continue refactoring
further refactorings
remove redundant code
end of the refactorings
expected a negative number to cause a cockup
negative numbers not allowed
haven't got the correct message
grief with syntax, but now passes