testsuite: add system recovery test

Problem: there are no tests for system instance recovery.

Add system/0004-recovery.t.

t/Makefile.am

@@ -286,6 +286,7 @@ dist_check_SCRIPTS = \
 	system/0001-basic.t \
 	system/0002-job-exec-sdexec-basic.t \
 	system/0003-instance-restart.t \
+	system/0004-recovery.t \
 	issues/t0441-kvs-put-get.sh \
 	issues/t0505-msg-handler-reg.lua \
 	issues/t0821-kvs-segfault.sh \

t/system/0004-recovery.t

@@ -0,0 +1,22 @@
+#
+#  Ensure flux start --recover works on the system instance
+#
+
+test_expect_success 'dump the last checkpoint' '
+        sudo -u flux flux dump --checkpoint /tmp/dump.tar
+'
+test_expect_success 'flux start --recover fails when instance is running' '
+	test_must_fail sudo -u flux flux start --recover /bin/true
+'
+test_expect_success 'stop the system instance' '
+	sudo flux shutdown
+'
+test_expect_success 'flux start --recover works' '
+	sudo -u flux flux start --recover /bin/true
+'
+test_expect_success 'flux start --recover works from dump file' '
+	sudo -u flux flux start --recover=/tmp/dump.tar --sysconfig /bin/true
+'
+test_expect_success 'restart flux' '
+        sudo systemctl start flux
+'