feat: units tests for checks lib (#5443)

Co-authored-by: Darragh Elliott <me@delliott.net>
Reviewed-on: #5443

build/fsfe_website_build_tests/lib/checks_test.py

@@ -0,0 +1,81 @@
+# SPDX-FileCopyrightText: Free Software Foundation Europe e.V. <https://fsfe.org>
+#
+# SPDX-License-Identifier: GPL-3.0-or-later
+import tempfile
+from collections.abc import Generator
+from pathlib import Path
+
+import pytest
+from fsfe_website_build.lib.checks import compare_elements, compare_files
+from lxml import etree
+
+
+class TestCompareFiles:
+    """Smoke tests for the high-level entry point."""
+
+    @pytest.fixture
+    def two_files(self) -> Generator[tuple[Path, Path]]:
+        """Yield two temporary XML files with different content."""
+        with tempfile.TemporaryDirectory() as tmpdir:
+            a = Path(tmpdir) / "a.xml"
+            b = Path(tmpdir) / "b.xml"
+            a.write_text("<root><x/></root>")
+            b.write_text("<root><y/></root>")
+            yield a, b
+
+    def test_compare_files_returns_list(self, two_files: tuple[Path, Path]) -> None:
+        a, b = two_files
+        assert isinstance(compare_files(a, b), list)
+
+    def test_compare_files_finds_difference(self, two_files: tuple[Path, Path]) -> None:
+        a, b = two_files
+        diff = compare_files(a, b)
+        assert len(diff) == 1
+
+
+class TestCompareElements:
+    """Unit tests for the xml comparator function"""
+
+    def identical_elements_test(self) -> None:
+        e1 = etree.Element("root")
+        e2 = etree.Element("root")
+        assert compare_elements(e1, e2) == []
+
+    def tag_mismatch_test(self) -> None:
+        e1 = etree.Element("root")
+        e2 = etree.Element("other")
+        diff = compare_elements(e1, e2)
+        assert len(diff) == 1
+
+    def attribute_delta_test(self) -> None:
+        e1 = etree.Element("root", a="1")
+        e2 = etree.Element("root", b="1")
+        diff = compare_elements(e1, e2)
+        assert len(diff) == 1
+
+    def attribute_value_diff_test(self) -> None:
+        e1 = etree.Element("root", x="1")
+        e2 = etree.Element("root", x="2")
+        diff = compare_elements(e1, e2)
+        assert len(diff) == 1
+
+    def whitelisted_attribute_ignored_test(self) -> None:
+        e1 = etree.Element("root", x="1")
+        e2 = etree.Element("root", x="2")
+        assert compare_elements(e1, e2, attr_whitelist={"x"}) == []
+
+    def child_count_mismatch_test(self) -> None:
+        e1 = etree.Element("root")
+        e1.append(etree.Element("a"))
+        e2 = etree.Element("root")
+        e2.extend([etree.Element("a"), etree.Element("b")])
+        diff = compare_elements(e1, e2)
+        assert len(diff) == 1
+
+    def deep_path_reporting_test(self) -> None:
+        root1 = etree.Element("root")
+        root1.append(etree.Element("child"))
+        root2 = etree.Element("root")
+        root2.append(etree.Element("other"))
+        diff = compare_elements(root1, root2)
+        assert len(diff) == 1