diff --git a/lib/common/tests/xml/Makefile.am b/lib/common/tests/xml/Makefile.am
index 5292980159..8db90c3100 100644
--- a/lib/common/tests/xml/Makefile.am
+++ b/lib/common/tests/xml/Makefile.am
@@ -1,23 +1,24 @@
#
# Copyright 2022-2024 the Pacemaker project contributors
#
# The version control history for this file may have further details.
#
# This source code is licensed under the GNU General Public License version 2
# or later (GPLv2+) WITHOUT ANY WARRANTY.
#
include $(top_srcdir)/mk/tap.mk
include $(top_srcdir)/mk/unittest.mk
# Add "_test" to the end of all test program names to simplify .gitignore.
check_PROGRAMS = pcmk__xe_copy_attrs_test \
pcmk__xe_first_child_test \
pcmk__xe_foreach_child_test \
pcmk__xe_set_score_test \
pcmk__xml_escape_test \
pcmk__xml_init_test \
+ pcmk__xml_is_name_char_test \
pcmk__xml_is_name_start_char_test \
pcmk__xml_needs_escape_test
TESTS = $(check_PROGRAMS)
diff --git a/lib/common/tests/xml/pcmk__xml_is_name_char_test.c b/lib/common/tests/xml/pcmk__xml_is_name_char_test.c
new file mode 100644
index 0000000000..49715a3c2e
--- /dev/null
+++ b/lib/common/tests/xml/pcmk__xml_is_name_char_test.c
@@ -0,0 +1,334 @@
+/*
+ * Copyright 2024 the Pacemaker project contributors
+ *
+ * The version control history for this file may have further details.
+ *
+ * This source code is licensed under the GNU General Public License version 2
+ * or later (GPLv2+) WITHOUT ANY WARRANTY.
+ */
+
+#include <crm_internal.h>
+
+#include <glib.h> // gchar, g_ascii_isalnum(), etc.
+
+#include <crm/common/unittest_internal.h>
+#include <crm/common/xml_internal.h>
+
+#include "crmcommon_private.h" // pcmk__xml_is_name_char()
+
+/*!
+ * \internal
+ * \brief Assert that a Unicode character is (not) a valid XML \c NameChar
+ *
+ * \param[in] c Unicode code point of character to check
+ * \param[in] reference If \c true, \p c should be considered a valid
+ * \c NameChar; if \c false, it should not
+ */
+static void
+assert_name_char(int c, bool reference)
+{
+ gchar utf8_buf[6] = { 0, };
+ int len = 4;
+ int ref_len = g_unichar_to_utf8(c, utf8_buf);
+ bool result = pcmk__xml_is_name_char(utf8_buf, &len);
+
+ if (reference) {
+ assert_true(result);
+ } else {
+ assert_false(result);
+ }
+
+ if ((c < 0xD800) || (c > 0xDFFF)) {
+ /* Unicode code points in the range D800 to DFFF are UTF-16 surrogate
+ * pair halves. They can be represented in UTF-8, but they shouldn't
+ * appear in valid UTF-8-encoded text. RFC 3629 (Nov 2003) says they
+ * should be treated as invalid:
+ * https://en.wikipedia.org/wiki/UTF-8#Invalid_sequences_and_error_handling.
+ *
+ * GLib treats these characters as valid and returns a length of 3
+ * bytes. So did libxml until v2.12 (commit 845bd99). Since that commit,
+ * libxml treats these characters as invalid and returns a length of 0.
+ * To avoid version-dependent testing behavior, skip the length check
+ * for code points in that range.
+ */
+ assert_int_equal(len, ref_len);
+ }
+}
+
+static void
+null_len(void **state)
+{
+ assert_true(pcmk__xml_is_name_char("a", NULL));
+ assert_false(pcmk__xml_is_name_char("@", NULL));
+}
+
+static void
+ascii(void **state)
+{
+ for (int c = 0x00; c <= 0x7F; c++) {
+ if (g_ascii_isalnum(c)
+ || c == ':' || c == '_' || c == '-' || c == '.') {
+
+ assert_name_char(c, true);
+ } else {
+ assert_name_char(c, false);
+ }
+ }
+}
+
+static void
+unicode_0x80_to_0xB6(void **state)
+{
+ for (int c = 0x80; c <= 0xB6; c++) {
+ assert_name_char(c, false);
+ }
+}
+
+static void
+unicode_0xB7(void **state)
+{
+ assert_name_char(0xB7, true);
+}
+
+static void
+unicode_0xB8_to_0xBF(void **state)
+{
+ for (int c = 0xB8; c <= 0xBF; c++) {
+ assert_name_char(c, false);
+ }
+}
+
+static void
+unicode_0xC0_to_0xD6(void **state)
+{
+ for (int c = 0xC0; c <= 0xD6; c++) {
+ assert_name_char(c, true);
+ }
+}
+
+static void
+unicode_0xD7(void **state)
+{
+ assert_name_char(0xD7, false);
+}
+
+static void
+unicode_0xD8_to_0xF6(void **state)
+{
+ for (int c = 0xD8; c <= 0xF6; c++) {
+ assert_name_char(c, true);
+ }
+}
+
+static void
+unicode_0xF7(void **state)
+{
+ assert_name_char(0xF7, false);
+}
+
+static void
+unicode_0xF8_to_0x2FF(void **state)
+{
+ for (int c = 0xF8; c <= 0x2FF; c++) {
+ assert_name_char(c, true);
+ }
+}
+
+static void
+unicode_0x300_to_0x36F(void **state)
+{
+ for (int c = 0x300; c <= 0x36F; c++) {
+ assert_name_char(c, true);
+ }
+}
+
+static void
+unicode_0x370_to_0x37D(void **state)
+{
+ for (int c = 0x370; c <= 0x37D; c++) {
+ assert_name_char(c, true);
+ }
+}
+
+static void
+unicode_0x37E(void **state)
+{
+ assert_name_char(0x37E, false);
+}
+
+static void
+unicode_0x37F_to_0x1FFF(void **state)
+{
+ for (int c = 0x37F; c <= 0x1FFF; c++) {
+ assert_name_char(c, true);
+ }
+}
+
+static void
+unicode_0x2000_to_0x200B(void **state)
+{
+ for (int c = 0x2000; c <= 0x200B; c++) {
+ assert_name_char(c, false);
+ }
+}
+
+static void
+unicode_0x200C_to_0x200D(void **state)
+{
+ for (int c = 0x200C; c <= 0x200D; c++) {
+ assert_name_char(c, true);
+ }
+}
+
+static void
+unicode_0x200E_to_0x203E(void **state)
+{
+ for (int c = 0x200E; c <= 0x203E; c++) {
+ assert_name_char(c, false);
+ }
+}
+
+static void
+unicode_0x203F_to_0x2040(void **state)
+{
+ for (int c = 0x203F; c <= 0x2040; c++) {
+ assert_name_char(c, true);
+ }
+}
+
+static void
+unicode_0x2041_to_0x206F(void **state)
+{
+ for (int c = 0x2041; c <= 0x206F; c++) {
+ assert_name_char(c, false);
+ }
+}
+
+static void
+unicode_0x2070_to_0x218F(void **state)
+{
+ for (int c = 0x2070; c <= 0x218F; c++) {
+ assert_name_char(c, true);
+ }
+}
+
+static void
+unicode_0x2190_to_0x2BFF(void **state)
+{
+ for (int c = 0x2190; c <= 0x2BFF; c++) {
+ assert_name_char(c, false);
+ }
+}
+
+static void
+unicode_0x2C00_to_0x2FEF(void **state)
+{
+ for (int c = 0x2C00; c <= 0x2FEF; c++) {
+ assert_name_char(c, true);
+ }
+}
+
+static void
+unicode_0x2FF0_to_0x3000(void **state)
+{
+ for (int c = 0x2FF0; c <= 0x3000; c++) {
+ assert_name_char(c, false);
+ }
+}
+
+static void
+unicode_0x3001_to_0xD7FF(void **state)
+{
+ for (int c = 0x3001; c <= 0xD7FF; c++) {
+ assert_name_char(c, true);
+ }
+}
+
+static void
+unicode_0xD800_to_0xF8FF(void **state)
+{
+ for (int c = 0xD800; c <= 0xF8FF; c++) {
+ assert_name_char(c, false);
+ }
+}
+
+static void
+unicode_0xF900_to_0xFDCF(void **state)
+{
+ for (int c = 0xF900; c <= 0xFDCF; c++) {
+ assert_name_char(c, true);
+ }
+}
+
+static void
+unicode_0xFDD0_to_0xFDEF(void **state)
+{
+ for (int c = 0xFDD0; c <= 0xFDEF; c++) {
+ assert_name_char(c, false);
+ }
+}
+
+static void
+unicode_0xFDF0_to_0xFFFD(void **state)
+{
+ for (int c = 0xFDF0; c <= 0xFFFD; c++) {
+ assert_name_char(c, true);
+ }
+}
+
+static void
+unicode_0xFFFE_to_0xFFFF(void **state)
+{
+ for (int c = 0xFFFE; c <= 0xFFFF; c++) {
+ assert_name_char(c, false);
+ }
+}
+
+static void
+unicode_0x10000_to_0xEFFFF(void **state)
+{
+ for (int c = 0x10000; c <= 0xEFFFF; c++) {
+ assert_name_char(c, true);
+ }
+}
+
+static void
+unicode_0xF0000_to_0x10FFFF(void **state)
+{
+ for (int c = 0xF0000; c <= 0x10FFFF; c++) {
+ assert_name_char(c, false);
+ }
+}
+
+PCMK__UNIT_TEST(NULL, NULL,
+ cmocka_unit_test(null_len),
+ cmocka_unit_test(ascii),
+ cmocka_unit_test(unicode_0x80_to_0xB6),
+ cmocka_unit_test(unicode_0xB7),
+ cmocka_unit_test(unicode_0xB8_to_0xBF),
+ cmocka_unit_test(unicode_0xC0_to_0xD6),
+ cmocka_unit_test(unicode_0xD7),
+ cmocka_unit_test(unicode_0xD8_to_0xF6),
+ cmocka_unit_test(unicode_0xF7),
+ cmocka_unit_test(unicode_0xF8_to_0x2FF),
+ cmocka_unit_test(unicode_0x300_to_0x36F),
+ cmocka_unit_test(unicode_0x370_to_0x37D),
+ cmocka_unit_test(unicode_0x37E),
+ cmocka_unit_test(unicode_0x37F_to_0x1FFF),
+ cmocka_unit_test(unicode_0x2000_to_0x200B),
+ cmocka_unit_test(unicode_0x200C_to_0x200D),
+ cmocka_unit_test(unicode_0x200E_to_0x203E),
+ cmocka_unit_test(unicode_0x203F_to_0x2040),
+ cmocka_unit_test(unicode_0x2041_to_0x206F),
+ cmocka_unit_test(unicode_0x2070_to_0x218F),
+ cmocka_unit_test(unicode_0x2190_to_0x2BFF),
+ cmocka_unit_test(unicode_0x2C00_to_0x2FEF),
+ cmocka_unit_test(unicode_0x2FF0_to_0x3000),
+ cmocka_unit_test(unicode_0x3001_to_0xD7FF),
+ cmocka_unit_test(unicode_0xD800_to_0xF8FF),
+ cmocka_unit_test(unicode_0xF900_to_0xFDCF),
+ cmocka_unit_test(unicode_0xFDD0_to_0xFDEF),
+ cmocka_unit_test(unicode_0xFDF0_to_0xFFFD),
+ cmocka_unit_test(unicode_0xFFFE_to_0xFFFF),
+ cmocka_unit_test(unicode_0x10000_to_0xEFFFF),
+ cmocka_unit_test(unicode_0xF0000_to_0x10FFFF))