test: introduce an integration test suite

Since we already use Packit, let's utilize its second part as well and
add a TMT [0] based integration test suite.

This PR add a second job to the existing Packit configuration, which
then sends the just built RPMs to Testing Farm [1] that executes all
selected tests (which currently means all discovered tests).

To demonstrate the functionality a bit, this PR also adds a simple test
case for polkit-org#439.

[0] https://tmt.readthedocs.io/en/stable/overview.html
[1] https://docs.testing-farm.io/Testing%20Farm/0.1/index.html

.packit.yaml

@@ -19,3 +19,10 @@ jobs:
   trigger: pull_request
   targets:
   - fedora-all
+
+- job: tests
+  trigger: pull_request
+  fmf_path: test/integration/
+  tmt_plan: upstream-ci
+  targets:
+  - fedora-all

test/integration/.fmf/version

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

test/integration/README

@@ -0,0 +1,54 @@
+# polkit integration test suite
+
+polkit'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/.../polkit/test/integration/test/name' created.
+Test metadata '/home/.../polkit/test/integration/test/name/main.fmf' created.
+Test script '/home/.../polkit/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/main.fmf

@@ -0,0 +1,2 @@
+require:
+  - polkit

test/integration/plans/upstream-ci.fmf

@@ -0,0 +1,11 @@
+# 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
+/:
+  inherit: false
+discover:
+  how: fmf
+execute:
+  how: tmt

test/integration/systemd/main.fmf

@@ -0,0 +1,2 @@
+summary: Check integration with systemd
+test: ./test.sh

test/integration/systemd/rules/start-restart-stop-unit.rules

@@ -0,0 +1,8 @@
+polkit.addRule(function(action, subject) {
+    if (action.id == "org.freedesktop.systemd1.manage-units") {
+        if (subject.user == "polkit-testuser" && action.lookup("unit") == "start-restart-stop.service" &&
+            (action.lookup("verb") == "restart" || action.lookup("verb") == "stop" || action.lookup("verb") == "start")) {
+            return polkit.Result.YES;
+        }
+    }
+});

test/integration/systemd/test.sh

@@ -0,0 +1,46 @@
+#!/bin/bash
+
+set -eux
+set -o pipefail
+
+TEST_RULES="$PWD/rules"
+TEST_USER="polkit-testuser"
+
+at_exit() {
+    set +e
+
+    : "Cleanup"
+    userdel -rf "$TEST_USER"
+    rm -f /etc/polkit-1/rules.d/99-test.rules
+    systemctl restart polkit
+}
+
+trap at_exit EXIT
+
+: "Setup"
+mkdir -p /run/systemd/system/
+useradd "$TEST_USER"
+# Close stdin, so we get an instant error (Interactive authentication required) instead of having to deal
+# with an interactive authentication prompt
+exec 0<&-
+
+: "Allow $TEST_USER to start/restart/stop a simple systemd unit"
+# Use `systemctl edit --full ...` in the future
+cat >/run/systemd/system/start-restart-stop.service <<EOF
+[Service]
+Type=oneshot
+ExecStart=true
+EOF
+systemctl daemon-reload
+# Copy the test polkit rule in place
+cp -fv "$TEST_RULES/start-restart-stop-unit.rules" /etc/polkit-1/rules.d/99-test.rules
+systemctl restart polkit
+# Following systemctl invocations should not trigger polkit's authentication prompt
+sudo -u "$TEST_USER" systemctl start start-restart-stop.service
+sudo -u "$TEST_USER" systemctl restart start-restart-stop.service
+sudo -u "$TEST_USER" systemctl stop start-restart-stop.service
+# But these ones should
+(! sudo -u "$TEST_USER" systemctl mask start-restart-stop.service)
+(! sudo -u "$TEST_USER" systemctl restart systemd-journald.service)
+# Cleanup
+rm -f /etc/polkit-1/rules.d/99-test.rules