Test covering non-tiny Uni -> Str handling.

All the other tests so far for NFG look at just a handful of codes;
this covers dealing with longer strings and Uni buffers.

S15-nfg/long-uni.t

@@ -0,0 +1,17 @@
+use Test;
+
+plan 24;
+
+for (10, 100, 1000, 10000) -> $n {
+    my @codes = (0x0044, 0x0307, 0x0323) xx $n;
+
+    my $s = Uni.new(@codes).Str;
+    is $s.chars, $n, 'long Uni -> Str works out';
+
+    my $nfc = $s.NFC;
+    is $nfc.codes, 2 * $n, 'long Str -> NFC works out';
+    is $nfc[0], 0x1E0C, 'NFC buffer has correct first value';
+    is $nfc[1], 0x307, 'NFC buffer has correct second value';
+    is $nfc[* - 2], 0x1E0C, 'NFC buffer has correct second-to-last value';
+    is $nfc[* - 1], 0x307, 'NFC buffer has correct last value';
+}