.beb and .json serialization of the document

tests/conftest.py

@@ -0,0 +1,37 @@
+"""Shared pytest fixtures for bedit tests.
+
+Qt-specific fixtures can be added here later when GUI testing starts. Keeping
+the model fixtures independent from Qt lets the core suite stay lightweight.
+"""
+
+from __future__ import annotations
+
+import pytest
+
+from bedit_core.models import (
+    Component,
+    ComponentID,
+    Document,
+    Graph,
+    GraphImplementation,
+    ID,
+    Interface,
+)
+
+
+@pytest.fixture
+def minimal_document() -> Document:
+    """Return the smallest useful graph document for core tests."""
+    root_id = ComponentID("root")
+    root = Component(
+        name="Root",
+        interface=Interface(),
+        parameters={},
+        implementation=GraphImplementation(Graph()),
+    )
+    return Document(
+        format_version=1,
+        id=ID("document"),
+        name="Test document",
+        root={root_id: root},
+    )