diff --git a/tests/test_validate_governance_assets.py b/tests/test_validate_governance_assets.py
new file mode 100644
index 0000000..a3a8519
--- /dev/null
+++ b/tests/test_validate_governance_assets.py
@@ -0,0 +1,81 @@
+from __future__ import annotations
+
+import importlib.util
+from pathlib import Path
+from types import SimpleNamespace
+
+
+def _load_module():
+    script_path = Path(__file__).resolve().parents[1] / "scripts" / "validate_governance_assets.py"
+    spec = importlib.util.spec_from_file_location("validate_governance_assets", script_path)
+    assert spec is not None
+    assert spec.loader is not None
+    module = importlib.util.module_from_spec(spec)
+    spec.loader.exec_module(module)
+    return module
+
+
+def test_is_policy_file_detects_ouroboros_policy_docs() -> None:
+    module = _load_module()
+    assert module.is_policy_file("docs/ouroboros/85_loss_recovery_action_plan.md")
+    assert not module.is_policy_file("docs/ouroboros/01_requirements_registry.md")
+    assert not module.is_policy_file("docs/workflow.md")
+    assert not module.is_policy_file("docs/ouroboros/notes.txt")
+
+
+def test_validate_registry_sync_requires_registry_update_when_policy_changes() -> None:
+    module = _load_module()
+    errors: list[str] = []
+    module.validate_registry_sync(
+        ["docs/ouroboros/85_loss_recovery_action_plan.md"],
+        errors,
+    )
+    assert errors
+    assert "policy file changed without updating" in errors[0]
+
+
+def test_validate_registry_sync_passes_when_registry_included() -> None:
+    module = _load_module()
+    errors: list[str] = []
+    module.validate_registry_sync(
+        [
+            "docs/ouroboros/85_loss_recovery_action_plan.md",
+            "docs/ouroboros/01_requirements_registry.md",
+        ],
+        errors,
+    )
+    assert errors == []
+
+
+def test_load_changed_files_supports_explicit_paths() -> None:
+    module = _load_module()
+    errors: list[str] = []
+    changed = module.load_changed_files(
+        ["./docs/ouroboros/85_loss_recovery_action_plan.md", " src/main.py "],
+        errors,
+    )
+    assert errors == []
+    assert changed == [
+        "docs/ouroboros/85_loss_recovery_action_plan.md",
+        "src/main.py",
+    ]
+
+
+def test_load_changed_files_with_range_uses_git_diff(monkeypatch) -> None:
+    module = _load_module()
+    errors: list[str] = []
+
+    def fake_run(cmd, check, capture_output, text):  # noqa: ANN001
+        assert cmd[:3] == ["git", "diff", "--name-only"]
+        assert check is True
+        assert capture_output is True
+        assert text is True
+        return SimpleNamespace(stdout="docs/ouroboros/85_loss_recovery_action_plan.md\nsrc/main.py\n")
+
+    monkeypatch.setattr(module.subprocess, "run", fake_run)
+    changed = module.load_changed_files(["abc...def"], errors)
+    assert errors == []
+    assert changed == [
+        "docs/ouroboros/85_loss_recovery_action_plan.md",
+        "src/main.py",
+    ]