test: integration tests

Let's follow-up on 0a0b0fa and introduce a second Packit job that runs
integration tests on the just built RPMs in Testing Farm [0].

The test organization and execution is handled by tmt [1]. To not
unnecessarily pollute the dbus-broker's git root, the tmt root is
initialized in the test/integration/ subdirectory (meaning that for the
tmt commands to work correctly you need to be somewhere below this
directory).

Since there are no pre-existing integration tests, add a simple one that
runs dfuzzer on the org.freedesktop.systemd1 D-Bus interface to
exercise dbus-broker a bit. A short README file is provided as well with
instructions on how to easily add a new test case, and with some links
where to find more information about tmt.

[0] https://packit.dev/docs/configuration/upstream/tests
[1] https://tmt.readthedocs.io/en/stable/overview.html

.packit.yml

@@ -1,5 +1,5 @@
 ---
-# vi:ts=2 sw=2 et:
+# vi: set ts=2 sw=2 et:
 #
 # Docs: https://packit.dev/docs/
 
@@ -35,8 +35,20 @@ jobs:
 - job: copr_build
   trigger: pull_request
   targets:
-  - fedora-all-aarch64
-  - fedora-all-i386
-  - fedora-all-ppc64le
-  - fedora-all-s390x
-  - fedora-all-x86_64
+    - fedora-all-aarch64
+    - fedora-all-i386
+    - fedora-all-ppc64le
+    - fedora-all-s390x
+    - fedora-all-x86_64
+
+- job: tests
+  trigger: pull_request
+  fmf_path: test/integration/
+  tmt_plan: upstream_ci
+  targets:
+    # Limit the Testing Farm jobs to the latest stable and rawhide releases to conserve resources
+    # See: https://packit.dev/docs/configuration#aliases
+    - fedora-latest-stable-aarch64
+    - fedora-latest-stable-x86_64
+    - fedora-rawhide-aarch64
+    - fedora-rawhide-x86_64

test/integration/.fmf/version

@@ -0,0 +1 @@
+1

test/integration/README

@@ -0,0 +1,54 @@
+# dbus-broker integration test suite
+
+dbus-broker's integration test suite uses tmt (Test Management Tool [0]) to organize and run tests. Since tmt
+offers a _lot_ of features, this document pinpoints the most _interesting_ ones to get stuff up and running
+quickly.
+
+## How to contribute
+
+Creating a new test case is pretty simple:
+
+```
+$ cd test/integration
+$ tmt test create --template=shell test/name
+Test directory '/home/.../dbus-broker/test/integration/test/name' created.
+Test metadata '/home/.../dbus-broker/test/integration/test/name/main.fmf' created.
+Test script '/home/.../dbus-broker/test/integration/test/name/test.sh' created.
+```
+
+The newly created `test.sh` will be the actual test case, and `main.fmf` contains the test metadata, including
+test summary & description, test dependencies, runtime, and so on. See [1] for more details.
+
+After tweaking the test metadata it's usually a good idea to run `tmt lint test/name` to make sure that the
+configuration is still valid:
+
+```
+$ tmt lint test/name
+/test/name
+pass C000 fmf node passes schema validation
+pass C001 summary key is set and is reasonably long
+...
+```
+
+To check if the test itself works as expected you can use `tmt run`:
+
+```
+$ cd test/name
+$ tmt run -vvv --all provision --how local tests --name .
+...
+total: 1 test passed
+```
+
+The `tmt run` command is _very_ customizable (as is the rest of `tmt`). In this particular example we tell it
+to run all steps (`--all`) and override the `provision` and `tests` steps to run just one particular test on
+the local machine. As in previous cases, check the `tmt` documentation [0] and examples [2] for more details.
+
+## Links
+
+[0] https://tmt.readthedocs.io/en/stable/overview.html
+
+[1] https://tmt.readthedocs.io/en/stable/spec/tests.html
+
+[2] https://tmt.readthedocs.io/en/stable/examples.html#run
+
+<!-- vim: set syntax=markdown tw=110 : -->

test/integration/fuzz/dfuzzer/main.fmf

@@ -0,0 +1,7 @@
+summary: Run dfuzzer on a couple of D-Bus interfaces
+test: ./test.sh
+recommend:
+    - dfuzzer
+    - systemd
+    - util-linux
+duration: 30m

test/integration/fuzz/dfuzzer/test.sh

@@ -0,0 +1,25 @@
+#!/bin/bash
+# vi: set sw=4 ts=4 et tw=110:
+
+set -eux
+set -o pipefail
+
+TEST_USER="dfuzzer$SRANDOM"
+
+at_exit() {
+    userdel -rf "$TEST_USER"
+}
+
+trap at_exit EXIT
+useradd "$TEST_USER"
+
+dbus-broker --version
+systemctl status --no-pager dbus-broker.service
+
+# Run dfuzzer on the PID 1's D-Bus interface. Drop privileges while doing so, since here we're interested in
+# the actual message broking instead of breaking systemd.
+#
+# org.freedesktop.systemd1 was picked here because its interface is very rich when it comes to function
+# signatures. Also, it's fuzzed in upstream by dfuzzer as well, which should make the test less prone to fails
+# due to issues on systemd's side.
+setpriv --reuid="$TEST_USER" --init-group -- dfuzzer -v --buffer-limit=10240 --bus org.freedesktop.systemd1

test/integration/plans/upstream_ci.fmf

@@ -0,0 +1,9 @@
+# vi: set sw=2 ts=2 et ft=yaml tw=80:
+
+# This plan discovers and executes all (enabled) integration tests
+
+summary: Upstream integration test suite
+discover:
+  how: fmf
+execute:
+  how: tmt