test-gunicode: add new test to show that unichar_iswide() is borked

I discovered this while looking at the tests with wide characters in the next
patch. It's something to fix, but not directly relevant to the issue of
skipping ANSI in ellipsization. We will generate output that is wider than
expected in some cases, but wide characters are used very rarely so this isn't
such a big problem.

src/test/meson.build

@@ -93,6 +93,7 @@ simple_tests += files(
         'test-fstab-util.c',
         'test-glob-util.c',
         'test-gpt.c',
+        'test-gunicode.c',
         'test-hash-funcs.c',
         'test-hexdecoct.c',
         'test-hmac.c',

src/test/test-gunicode.c

@@ -0,0 +1,27 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include "gunicode.h"
+#include "tests.h"
+#include "utf8.h"
+
+TEST(unichar_iswide) {
+        char32_t c;
+        int r;
+
+        /* FIXME: the cats are wide, but we get this wrong */
+        for (const char *narrow = "abX_…ąęµ!" "😼😿🙀😸😻"; *narrow; narrow += r) {
+                r = utf8_encoded_to_unichar(narrow, &c);
+                bool w = unichar_iswide(c);
+                assert_se(r > 0);
+                assert_se(!w);
+        }
+
+        for (const char *wide = "🐱／￥"; *wide; wide += r) {
+                r = utf8_encoded_to_unichar(wide, &c);
+                bool w = unichar_iswide(c);
+                assert_se(r > 0);
+                assert_se(w);
+        }
+}
+
+DEFINE_TEST_MAIN(LOG_INFO);