diff --git a/lib/common/tests/strings/Makefile.am b/lib/common/tests/strings/Makefile.am
index 06c9e392c1..9abb8e9a18 100644
--- a/lib/common/tests/strings/Makefile.am
+++ b/lib/common/tests/strings/Makefile.am
@@ -1,40 +1,41 @@
 #
 # Copyright 2020-2022 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 = \
 		crm_get_msec_test 	\
 		crm_is_true_test 	\
 		crm_str_to_boolean_test 	\
 		pcmk__add_word_test		\
 		pcmk__btoa_test			\
 		pcmk__char_in_any_str_test	\
 		pcmk__compress_test	\
 		pcmk__ends_with_test 		\
+		pcmk__g_strcat_test		\
 		pcmk__guint_from_hash_test	\
 		pcmk__numeric_strcasecmp_test \
 		pcmk__parse_ll_range_test	\
 		pcmk__s_test				\
 		pcmk__scan_double_test		\
 		pcmk__scan_min_int_test		\
 		pcmk__scan_port_test		\
 		pcmk__starts_with_test 		\
 		pcmk__str_any_of_test		\
 		pcmk__str_in_list_test		\
 		pcmk__str_table_dup_test	\
 		pcmk__str_update_test		\
 		pcmk__strcmp_test 			\
 		pcmk__strkey_table_test 	\
 		pcmk__strikey_table_test 	\
 		pcmk__trim_test
 
 TESTS = $(check_PROGRAMS)
diff --git a/lib/common/tests/strings/pcmk__g_strcat_test.c b/lib/common/tests/strings/pcmk__g_strcat_test.c
new file mode 100644
index 0000000000..7770075183
--- /dev/null
+++ b/lib/common/tests/strings/pcmk__g_strcat_test.c
@@ -0,0 +1,73 @@
+/*
+ * Copyright 2020-2022 the Pacemaker project contributors
+ *
+ * The version control history for this file may have further details.
+ *
+ * This source code is licensed under the GNU Lesser General Public License
+ * version 2.1 or later (LGPLv2.1+) WITHOUT ANY WARRANTY.
+ */
+
+#include <crm_internal.h>
+
+#include <crm/common/unittest_internal.h>
+
+static void
+add_to_null(void **state)
+{
+    pcmk__assert_asserts(pcmk__g_strcat(NULL, NULL));
+    pcmk__assert_asserts(pcmk__g_strcat(NULL, "hello", NULL));
+}
+
+static void
+add_nothing(void **state)
+{
+    GString *buf = g_string_new(NULL);
+
+    // Start with empty string
+    pcmk__g_strcat(buf, NULL);
+    assert_string_equal((const char *) buf->str, "");
+
+    pcmk__g_strcat(buf, "", NULL);
+    assert_string_equal((const char *) buf->str, "");
+
+    // Start with populated string
+    g_string_append(buf, "hello");
+    pcmk__g_strcat(buf, NULL);
+    assert_string_equal((const char *) buf->str, "hello");
+
+    pcmk__g_strcat(buf, "", NULL);
+    assert_string_equal((const char *) buf->str, "hello");
+    g_string_free(buf, TRUE);
+}
+
+static void
+add_words(void **state)
+{
+    GString *buf = g_string_new(NULL);
+
+    // Verify a call with multiple words
+    pcmk__g_strcat(buf, "hello", " ", NULL);
+    assert_string_equal((const char *) buf->str, "hello ");
+
+    // Verify that a second call doesn't overwrite the first one
+    pcmk__g_strcat(buf, "world", NULL);
+    assert_string_equal((const char *) buf->str, "hello world");
+    g_string_free(buf, TRUE);
+}
+
+static void
+stop_early(void **state)
+{
+    GString *buf = g_string_new(NULL);
+
+    // NULL anywhere after buf in the arg list should cause a return
+    pcmk__g_strcat(buf, "hello", NULL, " world", NULL);
+    assert_string_equal((const char *) buf->str, "hello");
+    g_string_free(buf, TRUE);
+}
+
+PCMK__UNIT_TEST(NULL, NULL,
+                cmocka_unit_test(add_to_null),
+                cmocka_unit_test(add_nothing),
+                cmocka_unit_test(add_words),
+                cmocka_unit_test(stop_early))