Added test for repeated group references.

Author: SimY4

core/src/test/scala/com/github/simy4/coregex/core/CoregexParserSuite.scala

@@ -64,6 +64,7 @@ class CoregexParserSuite extends ScalaCheckSuite with CoregexArbitraries {
       Pattern.compile("[a-z&&[^aeiou]]+[]][a-z&&aeiou&&ei]"),
       Pattern.compile("^(?:||)$"),
       Pattern.compile("<([A-Z][A-Z0-9]*)[^>]*>.*?</\\1>"),
+      Pattern.compile("(\\d+)(\\1)+"),
       Pattern.compile("(?!=.{10,}).+")
     ) ::: (if (scala.util.Properties.isJavaAtLeast(9)) {
              List(