ICU-22889 Addressed George's concerns.

icu4c/source/test/intltest/itrbnf.cpp

@@ -2623,11 +2623,12 @@ IntlTestRBNF::TestInfiniteRecursion() {
         if (U_SUCCESS(err)) {
             UnicodeString result;
             rbnf.format(5, result);
-            // we don't actually care about the result; we just want to make sure the function returns
+            // we don't actually care about the result and the function doesn't return an error code;
+            // we just want to make sure the function returns
 
             Formattable pResult;
             rbnf.parse("foo", pResult, err);
-            // we don't actually care about the result; we just want to make sure the function returns
+            assertTrue("rbnf.parse() didn't return U_INVALID_FORMAT_ERROR!", err = U_INVALID_FORMAT_ERROR);
         } else {
             // eventually it'd be nice to statically analyze the rules for (at least) the most common
             // causes of infinite recursion, in which case we'd end up down here and need to check

icu4j/main/common_tests/src/test/java/com/ibm/icu/dev/test/format/RbnfTest.java

@@ -1929,7 +1929,7 @@ public void TestInfiniteRecursion() {
 
             try {
                 rbnf.parse("foo");
-                // we don't actually care about the result; we just want to make sure the function returns
+                errln("Parse test didn't throw an exception!");
             } catch (IllegalStateException e) {
                 // we're supposed to get an IllegalStateException; swallow it and continue
             } catch (ParseException e) {