Add test for .uc/.lc with prepend codeponints. RT132020

Add a test to close RT132020. This test makes sure .uc works properly
even when a GCB=Prepend codepoint comes in front of it.

Author: samcv

S32-str/lc.t

@@ -2,7 +2,7 @@ use v6;
 
 use Test;
 
-plan 18;
+plan 19;
 
 # L<S32::Str/Str/lc>
 
@@ -40,4 +40,10 @@ is 'Σ'.lc, 'σ', 'final sigma does not apply if string is only an uppercase sig
 is 'The Σ is a Sigma'.lc, 'the σ is a sigma', 'final sigma does not apply if only letter in word (ws)';
 is 'Sigma looks like Σ.'.lc, 'sigma looks like σ.', 'final sigma does not apply if only letter in word (.)';
 
+# RT132020
+# This test makes sure .lc works properly even when a GCB=Prepend codepoint comes in front of it.
+{
+    is-deeply "\c[arabic number sign]A".lc, "\c[arabic number sign]a", "Uppercasing works even with prepend codepoints";
+}
+
 # vim: ft=perl6

S32-str/uc.t

@@ -2,7 +2,7 @@ use v6;
 
 use Test;
 
-plan 19;
+plan 20;
 
 # L<S32::Str/"Str"/=item uc>
 
@@ -61,5 +61,10 @@ is ~(0.lc),         ~0, '.lc on Int';
     #?rakudo.jvm todo 'got 3'
     is $s.uc.chars, 1, "Char with no precomposed upper gets NFG'd so upper is one grapheme";
 }
+# RT132020
+# This test makes sure .uc works properly even when a GCB=Prepend codepoint comes in front of it.
+{
+    is-deeply "\c[arabic number sign]a".uc, "\c[arabic number sign]A", "Uppercasing works even with prepend codepoints";
+}
 
 # vim: ft=perl6