[PATCH v2] oeqa/runtime/systemd: skip unit enable/disable on read-only-rootfs

["André Draszik" <git@andred.net>]

This doesn't work on read-only-rootfs:
    AssertionError: 1 != 0 : SYSTEMD_BUS_TIMEOUT=240s systemctl disable avahi-daemon.service
    Failed to disable unit: File /etc/systemd/system/multi-user.target.wants/avahi-daemon.service: Read-only file system

This patch does two things:
1) Decorate the existing test to be skipped if the rootfs is
   read-only
2) add a new test to be executed only if the rootfs is
   read-only. This new test remounts the rootfs read-write
   before continuing to execute the existing test, making
   sure to clean up correctly after itself (remount r/o
   again).

Signed-off-by: André Draszik <git@andred.net>

---
v2: We can do better by adding this 2nd test described above,
rather than just doing 1) described above
---
 meta/lib/oeqa/runtime/cases/systemd.py | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/meta/lib/oeqa/runtime/cases/systemd.py b/meta/lib/oeqa/runtime/cases/systemd.py
index c11fa49b07..7c44abe8ed 100644
--- a/meta/lib/oeqa/runtime/cases/systemd.py
+++ b/meta/lib/oeqa/runtime/cases/systemd.py
@@ -9,7 +9,7 @@ from oeqa.runtime.case import OERuntimeTestCase
 from oeqa.core.decorator.depends import OETestDepends
 from oeqa.core.decorator.data import skipIfDataVar, skipIfNotDataVar
 from oeqa.runtime.decorator.package import OEHasPackage
-from oeqa.core.decorator.data import skipIfNotFeature
+from oeqa.core.decorator.data import skipIfNotFeature, skipIfFeature
 
 class SystemdTest(OERuntimeTestCase):
 
@@ -114,12 +114,26 @@ class SystemdServiceTests(SystemdTest):
         self.systemctl('is-active', 'avahi-daemon.service', verbose=True)
 
     @OETestDepends(['systemd.SystemdServiceTests.test_systemd_status'])
+    @skipIfFeature('read-only-rootfs',
+                   'Test is only meant to run without read-only-rootfs in IMAGE_FEATURES')
     def test_systemd_disable_enable(self):
         self.systemctl('disable', 'avahi-daemon.service')
         self.systemctl('is-enabled', 'avahi-daemon.service', expected=1)
         self.systemctl('enable', 'avahi-daemon.service')
         self.systemctl('is-enabled', 'avahi-daemon.service')
 
+    @OETestDepends(['systemd.SystemdServiceTests.test_systemd_status'])
+    @skipIfNotFeature('read-only-rootfs',
+                      'Test is only meant to run with read-only-rootfs in IMAGE_FEATURES')
+    def test_systemd_disable_enable_ro(self):
+        status = self.target.run('mount -orw,remount /')[0]
+        self.assertTrue(status == 0, msg='Remounting / as r/w failed')
+        try:
+            self.test_systemd_disable_enable()
+        finally:
+            status = self.target.run('mount -oro,remount /')[0]
+            self.assertTrue(status == 0, msg='Remounting / as r/o failed')
+
 class SystemdJournalTests(SystemdTest):
 
     @OETestDepends(['systemd.SystemdBasicTests.test_systemd_basic'])
-- 
2.23.0.rc1