Add tests to reproduce issue #27

src/icalendar/tests/calendars/issue_27_multiple_periods.ics

@@ -0,0 +1,14 @@
+BEGIN:VCALENDAR
+VERSION:2.0
+PRODID:-//davmail.sf.net/NONSGML DavMail Calendar V1.1//EN
+METHOD:REPLY
+BEGIN:VFREEBUSY
+DTSTAMP:20120131T123000Z
+ORGANIZER:MAILTO:organizer@domain.tld
+DTSTART:20120101T000000Z
+DTEND:20120201T000000Z
+UID:null
+ATTENDEE:MAILTO:attendee@domain.tld
+FREEBUSY;FBTYPE=BUSY:20120103T091500Z/20120103T101500Z,20120113T130000Z/20120113T150000Z,20120116T130000Z/20120116T150000Z,20120117T091500Z/20120117T101500Z,20120118T160000Z/20120118T163000Z,20120124T083000Z/20120124T093000Z,20120124T123000Z/20120124T143000Z,20120131T091500Z/20120131T101500Z
+END:VFREEBUSY
+END:VCALENDAR

src/icalendar/tests/test_issue_27_period.py

@@ -0,0 +1,11 @@
+'''Issue #27 - multiple periods
+
+   https://github.com/collective/icalendar/issues/27
+'''
+from icalendar import Calendar
+
+def test_issue_27_multiple_periods(calendars):
+    free_busy = list(calendars.issue_27_multiple_periods.walk('VFREEBUSY'))
+    assert len(free_busy) == 1
+    
+