test: Add test for escaped semicolons in RRULEs

Author: frereit

calendar_test.go

@@ -341,6 +341,31 @@ ATTENDEE;CN=Test\;User:mailto:user@example.com
 CLASS:PUBLIC
 END:VEVENT
 END:VCALENDAR
+`,
+		},
+		{
+			name: "test RRULE escaping",
+			input: `BEGIN:VCALENDAR
+VERSION:2.0
+X-CUSTOM-FIELD:test
+PRODID:-//arran4//Golang ICS Library
+DESCRIPTION:test
+BEGIN:VEVENT
+RRULE:FREQ=YEARLY;BYMONTH=3;BYDAY=SU
+CLASS:PUBLIC
+END:VEVENT
+END:VCALENDAR
+`,
+			output: `BEGIN:VCALENDAR
+VERSION:2.0
+X-CUSTOM-FIELD:test
+PRODID:-//arran4//Golang ICS Library
+DESCRIPTION:test
+BEGIN:VEVENT
+RRULE:FREQ=YEARLY;BYMONTH=3;BYDAY=SU
+CLASS:PUBLIC
+END:VEVENT
+END:VCALENDAR
 `,
 		},
 	}