support/testing: add runtime test for easydbus

Test an actual D-Bus round-trip using easydbus:
 - obtain a name on the system bus
 - subscribe to a signal on a chosen object/interface
 - emit signal with a string payload
 - run the easydbus mainloop
 - verify the handler received the expected payload

This covers both the default Lua interpreter (Lua 5.4) and LuaJIT
(Lua 5.1 ABI).

Signed-off-by: Marcin Niestroj <m.niestroj@grinn-global.com>
[Julien:
 - move test files into a rootfs-overlay
 - move common BR2_PACKAGE_{,EASY}DBUS configs to EasyDBusBase
 - make stricter check of script output
 - add DEVELOPERS entry for rootfs-overlay files
]
Signed-off-by: Julien Olivain <ju.o@free.fr>

DEVELOPERS

@@ -2290,6 +2290,8 @@ F:	support/testing/tests/package/sample_python_dbus_fast.py
 F:	support/testing/tests/package/sample_python_dbus_next.py
 F:	support/testing/tests/package/sample_python_pytest.py
 F:	support/testing/tests/package/sample_python_pytest_asyncio.py
+F:	support/testing/tests/package/test_easydbus.py
+F:	support/testing/tests/package/test_easydbus/
 F:	support/testing/tests/package/test_netdata.py
 F:	support/testing/tests/package/test_python_dbus_next.py
 F:	support/testing/tests/package/test_python_pytest.py

support/testing/tests/package/test_easydbus.py

@@ -0,0 +1,44 @@
+import infra.basetest
+
+from tests.package.test_lua import TestLuaBase
+
+
+class EasyDBusBase(TestLuaBase):
+    rootfs_overlay = \
+        infra.filepath("tests/package/test_easydbus/rootfs-overlay")
+    config = TestLuaBase.config + \
+        f"""
+        BR2_PACKAGE_DBUS=y
+        BR2_PACKAGE_EASYDBUS=y
+        BR2_ROOTFS_OVERLAY="{rootfs_overlay}"
+        """
+
+    def signal_round_trip(self):
+        cmd = "lua /root/easydbus-sample.lua"
+        output, exit_code = self.emulator.run(cmd)
+        self.assertEqual(exit_code, 0)
+        self.assertEqual(output[0], "OK")
+
+
+class TestLuaEasyDBus(EasyDBusBase):
+    config = EasyDBusBase.config + \
+        """
+        BR2_PACKAGE_LUA=y
+        """
+
+    def test_run(self):
+        self.login()
+        self.module_test("easydbus")
+        self.signal_round_trip()
+
+
+class TestLuajitEasyDBus(EasyDBusBase):
+    config = EasyDBusBase.config + \
+        """
+        BR2_PACKAGE_LUAJIT=y
+        """
+
+    def test_run(self):
+        self.login()
+        self.module_test("easydbus")
+        self.signal_round_trip()

support/testing/tests/package/test_easydbus/rootfs-overlay/etc/dbus-1/system.d/easydbus.SampleTest.conf

@@ -0,0 +1,8 @@
+<!DOCTYPE busconfig PUBLIC "-//freedesktop//DTD D-BUS Bus Configuration 1.0//EN"
+ "http://www.freedesktop.org/standards/dbus/1.0/busconfig.dtd">
+<busconfig>
+  <policy user="root">
+    <allow own="easydbus.SampleTest"/>
+    <allow send_destination="easydbus.SampleTest"/>
+  </policy>
+</busconfig>

support/testing/tests/package/test_easydbus/rootfs-overlay/root/easydbus-sample.lua

@@ -0,0 +1,22 @@
+local dbus = require 'easydbus'
+
+local bus = assert(dbus.system())
+local service_name = 'easydbus.SampleTest'
+local object_path = '/easydbus/sample'
+local interface_name = 'easydbus.SampleTest'
+local signal_name = 'Pinged'
+
+local owner_id = assert(bus:own_name(service_name))
+
+local payload
+bus:subscribe(nil, object_path, interface_name, signal_name,
+              function(arg) payload = arg; dbus.mainloop_quit() end)
+assert(bus:emit(nil, object_path, interface_name, signal_name,
+                's', 'hello'))
+dbus.mainloop()
+
+bus:unown_name(owner_id)
+
+assert(payload == 'hello',
+       'unexpected payload: ' .. tostring(payload))
+print('OK')