I understood and fixed, but now other exception occurred "expected undefined to equal 'a'". The conditional the treat a first value is ok. So, I think when the value exists will be return the itself and not undefined or ' '.

That's because ' ' is indeed repeated (it's a space, not empty value)

There is a problem in the test, when doesn't match needed to return an 'undefined', but, in some test waiting an empty value ' ' instead of 'undefined'. This is weird. That is it?