stages: add new unit test for kickstart stage

This commit adds a simple and lightweight unit test for the new
kickstart options. It's pretty trivial but also cheap and runs
fast.

stages/test/org_osbuild_kickstart.py

@@ -0,0 +1 @@
+../org.osbuild.kickstart

stages/test/test_kickstart.py

@@ -0,0 +1,57 @@
+#!/usr/bin/python3
+
+import os
+import os.path
+import shutil
+import stat
+from tempfile import mkdtemp
+import unittest
+from unittest.mock import patch
+
+from org_osbuild_kickstart import main as kickstart_main
+
+test_cases = [
+    {
+        "options": {"lang": "en_US.UTF-8"},
+        "expected": "lang en_US.UTF-8",
+    },
+    {
+        "options": {"keyboard": "us"},
+        "expected": "keyboard us",
+    },
+    {
+        "options": {"timezone": "UTC"},
+        "expected": "timezone UTC",
+    },
+    {
+        "options": {
+            "lang": "en_US.UTF-8",
+            "keyboard": "us",
+            "timezone": "UTC",
+        },
+        "expected": "lang en_US.UTF-8\nkeyboard us\ntimezone UTC",
+    },
+    # TODO: add test cases for the existing options
+]
+
+
+class TestOrgOsbuilderKickstart(unittest.TestCase):
+
+    def setUp(self):
+        self.tmpdir = mkdtemp()
+        self.addCleanup(shutil.rmtree, self.tmpdir)
+
+    def test_kickstart(self):
+        ks_path = "kickstart/kfs.cfg"
+        for tc in test_cases:
+            options = {"path": ks_path}
+            options.update(tc["options"])
+            kickstart_main(self.tmpdir, options)
+
+            with open(os.path.join(self.tmpdir, ks_path)) as fp:
+                ks_content = fp.read()
+            self.assertEqual(ks_content, tc["expected"] + "\n")
+
+
+if __name__ == "__main__":
+    unittest.main()