Fix case-insensitive test generation with Unicodes

This excludes from testing the strings containing Unicode chars that
change length when changing case.

Author: bpintea

muted-tests.yml

@@ -498,36 +498,6 @@ tests:
 - class: org.elasticsearch.xpack.esql.expression.function.scalar.string.WildcardLikeTests
   method: testEvaluateInManyThreads {TestCase=100 random code points matches self case insensitive with text}
   issue: https://github.com/elastic/elasticsearch/issues/128677
-- class: org.elasticsearch.xpack.esql.expression.function.scalar.string.RLikeTests
-  method: testEvaluateInManyThreads {TestCase=100 random code points matches self case insensitive with text}
-  issue: https://github.com/elastic/elasticsearch/issues/128705
-- class: org.elasticsearch.xpack.esql.expression.function.scalar.string.RLikeTests
-  method: testEvaluateInManyThreads {TestCase=100 random code points matches self case insensitive with keyword}
-  issue: https://github.com/elastic/elasticsearch/issues/128706
-- class: org.elasticsearch.xpack.esql.expression.function.scalar.string.RLikeTests
-  method: testCrankyEvaluateBlockWithNulls {TestCase=100 random code points matches self case insensitive with text}
-  issue: https://github.com/elastic/elasticsearch/issues/128710
-- class: org.elasticsearch.xpack.esql.expression.function.scalar.string.RLikeTests
-  method: testCrankyEvaluateBlockWithNulls {TestCase=100 random code points matches self case insensitive with keyword}
-  issue: https://github.com/elastic/elasticsearch/issues/128711
-- class: org.elasticsearch.xpack.esql.expression.function.scalar.string.WildcardLikeTests
-  method: testCrankyEvaluateBlockWithNulls {TestCase=100 random code points matches self case insensitive with text}
-  issue: https://github.com/elastic/elasticsearch/issues/128712
-- class: org.elasticsearch.xpack.esql.expression.function.scalar.string.WildcardLikeTests
-  method: testCrankyEvaluateBlockWithNulls {TestCase=100 random code points matches self case insensitive with keyword}
-  issue: https://github.com/elastic/elasticsearch/issues/128713
-- class: org.elasticsearch.xpack.esql.expression.function.scalar.string.WildcardLikeTests
-  method: testEvaluateBlockWithNulls {TestCase=100 random code points matches self case insensitive with text}
-  issue: https://github.com/elastic/elasticsearch/issues/128714
-- class: org.elasticsearch.xpack.esql.expression.function.scalar.string.WildcardLikeTests
-  method: testEvaluateBlockWithNulls {TestCase=100 random code points matches self case insensitive with keyword}
-  issue: https://github.com/elastic/elasticsearch/issues/128715
-- class: org.elasticsearch.xpack.esql.expression.function.scalar.string.RLikeTests
-  method: testEvaluateBlockWithNulls {TestCase=100 random code points matches self case insensitive with keyword}
-  issue: https://github.com/elastic/elasticsearch/issues/128716
-- class: org.elasticsearch.xpack.esql.expression.function.scalar.string.RLikeTests
-  method: testEvaluateBlockWithNulls {TestCase=100 random code points matches self case insensitive with text}
-  issue: https://github.com/elastic/elasticsearch/issues/128717
 - class: org.elasticsearch.compute.operator.LimitOperatorTests
   method: testEarlyTermination
   issue: https://github.com/elastic/elasticsearch/issues/128721

x-pack/plugin/esql/src/test/java/org/elasticsearch/xpack/esql/expression/function/scalar/string/RLikeTests.java

@@ -94,8 +94,15 @@ private static void casesForString(
             return new TextAndPattern(text, escapeString.apply(text));
         }, true);
         cases(cases, title + " matches self case insensitive", () -> {
-            String text = textSupplier.get();
-            return new TextAndPattern(randomCasing(text), escapeString.apply(text));
+            // RegExp doesn't support case-insensitive matching for Unicodes whose length changes when the case changes.
+            // Example: a case-insensitive ES regexp query for the pattern `weiß` won't match the value `WEISS` (but will match `WEIß`).
+            // Or `ʼn` (U+0149) vs. `ʼN` (U+02BC U+004E).
+            String text, caseChanged;
+            for (text = textSupplier.get(), caseChanged = randomCasing(text); text.length() != caseChanged.length(); ) {
+                text = textSupplier.get();
+                caseChanged = randomCasing(text);
+            }
+            return new TextAndPattern(caseChanged, escapeString.apply(text));
         }, true, true);
         cases(cases, title + " doesn't match self with trailing", () -> {
             String text = textSupplier.get();