This should also fix #311 now. While working on the escaping of the CDATA sections I noticed the problem is more widespread. We also need to escape those parts where file names, test names, or skip messages are inserted, as they might contain characters that break the xml.

Hence, I opted for using xml escape sequences like < instead of the CDATA only solution.

I've added a commit, this looks great.

One question is flag names, currently --formatter and --report. Should the latter be --reporter?

I also think the -help text has got messy, I'll get round to cleaning that up.

Yes, I also thought about that but reporter is a loaded word. If we are okay with a long name I would opt for --report-format[ter].

I just noticed that there is a problem when we want to use a report formatter that uses the internal extended syntax and the tap formatter which simply forwards the input. We can either forbid this combination or we have to implement a filter function on the tap formatter or we live with the invalid tap output.

I made the TAP formatter compatible with extended syntax. For this I added lib/bats-core/formatter.bash to centralize the parsing logic and use callbacks for the individual formatters. I only implemented this for tap and pretty, we should move the others over to this interface as well.

In the long run this offers the opportunity to check if the formatters implement the interface correctly by at least having a definition of these callbacks, which might pave the way for a stable interface to move formatters out of bats-core.

@sublimino You can review now.