Initial commit: stateful OpenStack API laboratory simulator.

Ship Keystone auth, multi-service handlers (Yoga→Dalmatian), Compose/Helm
packaging, API contract packs, and pytest/Pulumi coverage labs.

tests/unit/test_contract_diff.py

@@ -0,0 +1,87 @@
+"""Semantic contract diff classification and rendering tests."""
+
+import json
+from datetime import UTC, datetime
+
+from app.contracts.diff import (
+    Severity,
+    compare_snapshots,
+    has_breaking_changes,
+    render_html,
+    render_json,
+    render_markdown,
+    render_text,
+)
+from app.contracts.model import Method, PathContract, Schema, Snapshot
+
+
+def snapshot(paths: tuple[PathContract, ...]) -> Snapshot:
+    return Snapshot(
+        source_version="test",
+        retrieved_at=datetime(2026, 1, 1, tzinfo=UTC),
+        raw_sha256="0" * 64,
+        paths=paths,
+        path_count=len(paths),
+        method_count=sum(len(path.methods) for path in paths),
+    )
+
+
+def method(description: str = "old", returns: Schema | None = None) -> Method:
+    return Method(
+        verb="GET",
+        name="read",
+        description=description,
+        returns=returns or Schema(type="string"),
+        checksum="1" * 64,
+    )
+
+
+def test_classifies_added_removed_and_changed_contracts() -> None:
+    before = snapshot(
+        (
+            PathContract(path="/removed", methods=(method(),)),
+            PathContract(path="/version", methods=(method(),)),
+        )
+    )
+    after = snapshot(
+        (
+            PathContract(path="/added", methods=(method(),)),
+            PathContract(
+                path="/version",
+                methods=(method("new", Schema(type="integer", minimum=1)),),
+            ),
+        )
+    )
+
+    changes = compare_snapshots(before, after)
+
+    assert changes == tuple(sorted(changes))
+    assert {change.category for change in changes} >= {
+        "path",
+        "method",
+        "documentation",
+        "schema",
+        "constraint",
+    }
+    assert has_breaking_changes(changes)
+    assert any(change.severity is Severity.NON_BREAKING for change in changes)
+
+
+def test_renderers_are_stable_and_escape_html() -> None:
+    before = snapshot((PathContract(path="/<old>", methods=(method(),)),))
+    after = snapshot(())
+    changes = compare_snapshots(before, after)
+
+    assert render_text(changes).startswith("breaking:")
+    assert "| breaking |" in render_markdown(changes)
+    assert "&lt;old&gt;" in render_html(changes)
+    decoded = json.loads(render_json(changes))
+    assert decoded[0]["severity"] == "breaking"
+    assert render_json(changes) == render_json(changes)
+
+
+def test_no_changes_has_clean_ci_policy() -> None:
+    value = snapshot((PathContract(path="/version", methods=(method(),)),))
+
+    assert compare_snapshots(value, value) == ()
+    assert not has_breaking_changes(())