Extend unit test for org.osbuild.grub2 stage

Test the content of the /etc/default/grub config file based on the
provided stage options.

Signed-off-by: Tomáš Hozza <thozza@redhat.com>

stages/test/test_grub2.py

@@ -1,5 +1,9 @@
 #!/usr/bin/python3
 
+import os.path
+
+import pytest
+
 from osbuild.testutil import make_fake_tree
 
 STAGE_NAME = "org.osbuild.grub2"
@@ -26,3 +30,54 @@ def test_grub2_copy_efi_data(tmp_path, stage_module):
     stage_module.main(fake_tree, test_options)
     assert (fake_tree / "boot/efi/EFI/fedora/a.shim").exists()
     assert (fake_tree / "boot/efi/EFI/BOOT/BOOTX64.EFI").exists()
+
+
+# Test that the /etc/default/grub file is created with the correct content
+@pytest.mark.parametrize("test_data,expected_conf", [
+    # default
+    ({}, """GRUB_CMDLINE_LINUX=""
+GRUB_TIMEOUT=0
+GRUB_ENABLE_BLSCFG=true
+"""),
+    # custom
+    ({
+        "default": "0",
+        "timeout": 10,
+        "terminal_input": ["console"],
+        "terminal_output": ["serial"],
+        "serial": "serial --speed=115200 --unit=0 --word=8 --parity=no --stop=1",
+    }, """GRUB_CMDLINE_LINUX=""
+GRUB_TIMEOUT=10
+GRUB_ENABLE_BLSCFG=true
+GRUB_SERIAL_COMMAND="serial --speed=115200 --unit=0 --word=8 --parity=no --stop=1"
+GRUB_TERMINAL_INPUT="console"
+GRUB_TERMINAL_OUTPUT="serial"
+GRUB_DEFAULT=0
+"""),
+])
+def test_grub2_default_conf(tmp_path, stage_module, test_data, expected_conf):
+    treedir = tmp_path / "tree"
+    confpath = treedir / "etc/default/grub"
+    confpath.parent.mkdir(parents=True, exist_ok=True)
+
+    options = {
+        "rootfs": {
+            "label": "root"
+        },
+        "entries": [
+            {
+                "id": "fff",
+                "kernel": "4.18",
+                "product": {
+                    "name": "Fedora",
+                    "version": "40"
+                }
+            }
+        ]
+    }
+
+    options["config"] = test_data
+    stage_module.main(treedir, options)
+
+    assert os.path.exists(confpath)
+    assert confpath.read_text() == expected_conf