diff --git a/lib/common/tests/output/Makefile.am b/lib/common/tests/output/Makefile.am
index d3a90207bc..5c78e8cfd4 100644
--- a/lib/common/tests/output/Makefile.am
+++ b/lib/common/tests/output/Makefile.am
@@ -1,23 +1,24 @@
 #
 # Copyright 2021-2022 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.
 #
 
 AM_CPPFLAGS = -I$(top_srcdir)/include		\
 	      -I$(top_builddir)/include		\
 	      -I$(top_srcdir)/lib/common
 LDADD = $(top_builddir)/lib/common/libcrmcommon_test.la \
 		-lcmocka
 AM_CFLAGS = -DPCMK__UNIT_TESTING
 AM_LDFLAGS = $(LDFLAGS_WRAP)
 
 include $(top_srcdir)/mk/tap.mk
 
 # Add "_test" to the end of all test program names to simplify .gitignore.
-check_PROGRAMS =	pcmk__register_format_test
+check_PROGRAMS =	pcmk__register_format_test \
+					pcmk__register_formats_test
 
 TESTS = $(check_PROGRAMS)
diff --git a/lib/common/tests/output/pcmk__register_formats_test.c b/lib/common/tests/output/pcmk__register_formats_test.c
new file mode 100644
index 0000000000..6d34b5e187
--- /dev/null
+++ b/lib/common/tests/output/pcmk__register_formats_test.c
@@ -0,0 +1,116 @@
+/*
+ * Copyright 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>
+#include <crm/common/output_internal.h>
+
+static pcmk__output_t *
+null_create_fn(char **argv) {
+    return NULL;
+}
+
+static pcmk__output_t *
+null_create_fn_2(char **argv) {
+    return NULL;
+}
+
+static void
+no_formats(void **state) {
+    pcmk__register_formats(NULL, NULL);
+    assert_null(pcmk__output_formatters());
+}
+
+static void
+invalid_entries(void **state) {
+    /* Here, we can only test that an empty name won't be added.  A NULL name is
+     * the marker for the end of the format table.
+     */
+    pcmk__supported_format_t formats[] = {
+        { "", null_create_fn, NULL },
+        { NULL },
+    };
+
+    pcmk__assert_asserts(pcmk__register_formats(NULL, formats));
+}
+
+static void
+valid_entries(void **state) {
+    GHashTable *formatters = NULL;
+
+    pcmk__supported_format_t formats[] = {
+        { "fmt1", null_create_fn, NULL },
+        { "fmt2", null_create_fn_2, NULL },
+        { NULL },
+    };
+
+    pcmk__register_formats(NULL, formats);
+
+    formatters = pcmk__output_formatters();
+    assert_int_equal(g_hash_table_size(formatters), 2);
+    assert_ptr_equal(g_hash_table_lookup(formatters, "fmt1"), null_create_fn);
+    assert_ptr_equal(g_hash_table_lookup(formatters, "fmt2"), null_create_fn_2);
+
+    pcmk__unregister_formats();
+}
+
+static void
+duplicate_keys(void **state) {
+    GHashTable *formatters = NULL;
+
+    pcmk__supported_format_t formats[] = {
+        { "fmt1", null_create_fn, NULL },
+        { "fmt1", null_create_fn_2, NULL },
+        { NULL },
+    };
+
+    pcmk__register_formats(NULL, formats);
+
+    formatters = pcmk__output_formatters();
+    assert_int_equal(g_hash_table_size(formatters), 1);
+    assert_ptr_equal(g_hash_table_lookup(formatters, "fmt1"), null_create_fn_2);
+
+    pcmk__unregister_formats();
+}
+
+static void
+duplicate_values(void **state) {
+    GHashTable *formatters = NULL;
+
+    pcmk__supported_format_t formats[] = {
+        { "fmt1", null_create_fn, NULL },
+        { "fmt2", null_create_fn, NULL },
+        { NULL },
+    };
+
+    pcmk__register_formats(NULL, formats);
+
+    formatters = pcmk__output_formatters();
+    assert_int_equal(g_hash_table_size(formatters), 2);
+    assert_ptr_equal(g_hash_table_lookup(formatters, "fmt1"), null_create_fn);
+    assert_ptr_equal(g_hash_table_lookup(formatters, "fmt2"), null_create_fn);
+
+    pcmk__unregister_formats();
+}
+
+int
+main(int argc, char **argv)
+{
+    const struct CMUnitTest tests[] = {
+        cmocka_unit_test(no_formats),
+        cmocka_unit_test(invalid_entries),
+        cmocka_unit_test(valid_entries),
+        cmocka_unit_test(duplicate_keys),
+        cmocka_unit_test(duplicate_values),
+    };
+
+    cmocka_set_message_output(CM_OUTPUT_TAP);
+    return cmocka_run_group_tests(tests, NULL, NULL);
+}