diff --git a/lib/common/tests/xml/Makefile.am b/lib/common/tests/xml/Makefile.am
index 3aa600d645..db0cbaa120 100644
--- a/lib/common/tests/xml/Makefile.am
+++ b/lib/common/tests/xml/Makefile.am
@@ -1,25 +1,26 @@
 #
 # 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_id_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	\
 		 pcmk__xml_sanitize_id_test
 
 TESTS = $(check_PROGRAMS)
diff --git a/lib/common/tests/xml/pcmk__xe_set_id_test.c b/lib/common/tests/xml/pcmk__xe_set_id_test.c
new file mode 100644
index 0000000000..8c7f6c19e8
--- /dev/null
+++ b/lib/common/tests/xml/pcmk__xe_set_id_test.c
@@ -0,0 +1,102 @@
+/*
+ * 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 <crm/common/unittest_internal.h>
+#include <crm/common/xml_internal.h>
+
+static void
+null_node(void **state)
+{
+    pcmk__xe_set_id(NULL, "test_id");
+}
+
+static void
+null_format(void **state)
+{
+    xmlNode *test_xml = pcmk__xe_create(NULL, "test");
+
+    pcmk__assert_asserts(pcmk__xe_set_id(NULL, NULL));
+    pcmk__assert_asserts(pcmk__xe_set_id(test_xml, NULL));
+
+#ifdef HAVE_FORMAT_NONLITERAL
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wformat-zero-length"
+#endif  // HAVE_FORMAT_NONLITERAL
+    pcmk__assert_asserts(pcmk__xe_set_id(test_xml, ""));
+#ifdef HAVE_FORMAT_NONLITERAL
+#pragma GCC diagnostic pop
+#endif  // HAVE_FORMAT_NONLITERAL
+
+    pcmk__xml_free(test_xml);
+}
+
+static void
+valid_id(void **state)
+{
+    // IDs that are already valid XML names
+    xmlNode *test_xml = pcmk__xe_create(NULL, "test");
+    const char *id = NULL;
+
+    // No ID set initially
+    pcmk__xe_set_id(test_xml, "test_id");
+    assert_string_equal(pcmk__xe_id(test_xml), "test_id");
+
+    // ID already set: test overwrite
+    // #xEFFFF (NameStartChar), #xB7 (NameChar)
+    id = "\xF3\xAF\xBF\xBF" "\xC2\xB7";
+    pcmk__xe_set_id(test_xml, "%s", id);
+    assert_string_equal(pcmk__xe_id(test_xml), id);
+
+    pcmk__xml_free(test_xml);
+}
+
+static void
+invalid_id(void **state)
+{
+    // IDs that need sanitization
+    xmlNode *test_xml = pcmk__xe_create(NULL, "test");
+
+    // No ID set initially
+    pcmk__xe_set_id(test_xml, "-ab");
+    assert_string_equal(pcmk__xe_id(test_xml), "_ab");
+
+    // ID already set: test overwrite
+    pcmk__xe_set_id(test_xml, "a$b");
+    assert_string_equal(pcmk__xe_id(test_xml), "a.b");
+
+    pcmk__xe_set_id(test_xml, "ab$");
+    assert_string_equal(pcmk__xe_id(test_xml), "ab.");
+
+    pcmk__xe_set_id(test_xml, "$$$");
+    assert_string_equal(pcmk__xe_id(test_xml), "_..");
+
+    pcmk__xml_free(test_xml);
+}
+
+static void
+format_args(void **state)
+{
+    xmlNode *test_xml = pcmk__xe_create(NULL, "test");
+    const char *str = "test";
+    int num = 42;
+
+    pcmk__xe_set_id(test_xml, "rsc-%s-%d", str, num);
+    assert_string_equal(pcmk__xe_id(test_xml), "rsc-test-42");
+
+    pcmk__xml_free(test_xml);
+}
+
+PCMK__UNIT_TEST(pcmk__xml_test_setup_group, pcmk__xml_test_teardown_group,
+                cmocka_unit_test(null_node),
+                cmocka_unit_test(null_format),
+                cmocka_unit_test(valid_id),
+                cmocka_unit_test(invalid_id),
+                cmocka_unit_test(format_args))