Custom matchers

Here's a quick overview of the matchers introduced for specs in this project.

Integration tests

These matchers are available in integration specs (see integration directory):

warn_with(line0, line1...) checks that warnings containing line0 etc have been emitted,
report_with(line0, line1...) checks that messages containing line0 etc have been reported to the user,
have_empty_report checks that no messages have been reported to the user,
ask(question) checks that the user has been prompted for the string question.