Creating unit tests using GTestDBus

Testing of D-Bus services can be tricky because normally we only ever run D-Bus services over an existing instance of the D-Bus daemon thus we usually don't activate D-Bus services that are not yet installed into the target system. The GTestDBus object makes this easier for us by taking care of the lower level tasks such as running a private D-Bus daemon and looking up uninstalled services in customizable locations, typically in your source code tree.

The first thing you will need is a separate service description file for the D-Bus daemon. Typically a services subdirectory of your tests directory is a good place to put this file.

The service file should list your service along with an absolute path to the uninstalled service executable in your source tree. Using autotools we would achieve this by adding a file such as my-server.service.in in the services directory and have it processed by configure.

1
2
3

[D-BUS Service]
Name=org.gtk.GDBus.Examples.ObjectManager
Exec=@abs_top_builddir@/gio/tests/gdbus-example-objectmanager-server

You will also need to indicate this service directory in your test fixtures, so you will need to pass the path while compiling your test cases. Typically this is done with autotools with an added preprocessor flag specified to compile your tests such as:

1

-DTEST_SERVICES=\""$(abs_top_builddir)/tests/services"\"

Once you have a service definition file which is local to your source tree, you can proceed to set up a GTest fixture using the GTestDBus scaffolding.

An example of a test fixture for D-Bus services can be found here: gdbus-test-fixture.c

Note that these examples only deal with isolating the D-Bus aspect of your service. To successfully run isolated unit tests on your service you may need some additional modifications to your test case fixture. For example; if your service uses GSettings and installs a schema then it is important that your test service not load the schema in the ordinary installed location (chances are that your service and schema files are not yet installed, or worse; there is an older version of the schema file sitting in the install location).

Most of the time we can work around these obstacles using the environment. Since the environment is inherited by the D-Bus daemon created by GTestDBus and then in turn inherited by any services the D-Bus daemon activates, using the setup routine for your fixture is a practical place to help sandbox your runtime environment. For the rather typical GSettings case we can work around this by setting GSETTINGS_SCHEMA_DIR to the in tree directory holding your schemas in the above fixture_setup() routine.

The GSettings schemas need to be locally pre-compiled for this to work. This can be achieved by compiling the schemas locally as a step before running test cases, an autotools setup might do the following in the directory holding schemas:

1
2
3
4

all-am:
        $(GLIB_COMPILE_SCHEMAS) .

CLEANFILES += gschemas.compiled

g_test_dbus_new ()

GTestDBus *
g_test_dbus_new (GTestDBusFlags flags);

Create a new GTestDBus object.

g_test_dbus_get_flags ()

GTestDBusFlags
g_test_dbus_get_flags (GTestDBus *self);

Get the flags of the GTestDBus object.

g_test_dbus_get_bus_address ()

const gchar *
g_test_dbus_get_bus_address (GTestDBus *self);

Get the address on which dbus-daemon is running. If g_test_dbus_up() has not been called yet, NULL is returned. This can be used with g_dbus_connection_new_for_address().

g_test_dbus_add_service_dir ()

void
g_test_dbus_add_service_dir (GTestDBus *self,
                             const gchar *path);

Add a path where dbus-daemon will look up .service files. This can't be called after g_test_dbus_up().

g_test_dbus_up ()

void
g_test_dbus_up (GTestDBus *self);

Start a dbus-daemon instance and set DBUS_SESSION_BUS_ADDRESS. After this call, it is safe for unit tests to start sending messages on the session bus.

If this function is called from setup callback of g_test_add(), g_test_dbus_down() must be called in its teardown callback.

If this function is called from unit test's main(), then g_test_dbus_down() must be called after g_test_run().

g_test_dbus_stop ()

void
g_test_dbus_stop (GTestDBus *self);

Stop the session bus started by g_test_dbus_up().

Unlike g_test_dbus_down(), this won't verify the GDBusConnection singleton returned by g_bus_get() or g_bus_get_sync() is destroyed. Unit tests wanting to verify behaviour after the session bus has been stopped can use this function but should still call g_test_dbus_down() when done.

g_test_dbus_down ()

void
g_test_dbus_down (GTestDBus *self);

Stop the session bus started by g_test_dbus_up().

This will wait for the singleton returned by g_bus_get() or g_bus_get_sync() is destroyed. This is done to ensure that the next unit test won't get a leaked singleton from this test.

g_test_dbus_unset ()

void
g_test_dbus_unset (void);

Unset DISPLAY and DBUS_SESSION_BUS_ADDRESS env variables to ensure the test won't use user's session bus.

This is useful for unit tests that want to verify behaviour when no session bus is running. It is not necessary to call this if unit test already calls g_test_dbus_up() before acquiring the session bus.

GTestDBus

typedef struct _GTestDBus GTestDBus;

The GTestDBus structure contains only private data and should only be accessed using the provided API.

Since 2.34

enum GTestDBusFlags

Flags to define future GTestDBus behaviour.

Since 2.34

The “flags” property

  “flags”                    GTestDBusFlags

GTestDBusFlags specifying the behaviour of the D-Bus session.

Flags: Read / Write / Construct Only

Since 2.34