1 files changed, 71 insertions, 0 deletions
diff --git a/tests/test_models.py b/tests/test_models.py
new file mode 100644
index 0000000..2c678a0
--- /dev/null
+++ b/tests/test_models.py
@@ -0,0 +1,71 @@
+from __future__ import annotations
+
+import pytest
+from pydantic import ValidationError
+
+from gap_pipeline.models import (
+    DiffusedProof,
+    MethodPlan,
+    ProofDAG,
+    ReplacementSpec,
+)
+
+
+def test_valid_dag_and_plan(dag_dict: dict, plan_dict: dict) -> None:
+    dag = ProofDAG.model_validate(dag_dict)
+    assert [node.node_id for node in dag.topological_nodes()] == ["n1", "n2"]
+    assert dag.leaf_node_ids() == ["n1"]
+    plan = MethodPlan.model_validate(plan_dict)
+    plan.validate_against(dag)
+
+
+def test_cycle_is_rejected(dag_dict: dict) -> None:
+    dag_dict["nodes"][0]["dependencies"] = ["n2"]
+    with pytest.raises(ValidationError, match="cycle"):
+        ProofDAG.model_validate(dag_dict)
+
+
+def test_node_disconnected_from_terminal_is_rejected(dag_dict: dict) -> None:
+    dag_dict["nodes"].append(
+        {
+            "node_id": "orphan",
+            "claim": "unused claim",
+            "derivation": "unused derivation",
+            "dependencies": [],
+            "source_span": "",
+            "mathematical_objects": [],
+        }
+    )
+    with pytest.raises(ValidationError, match="disconnected"):
+        ProofDAG.model_validate(dag_dict)
+
+
+def test_method_reordering_is_rejected(dag_dict: dict, plan_dict: dict) -> None:
+    dag = ProofDAG.model_validate(dag_dict)
+    plan_dict["steps"].reverse()
+    plan = MethodPlan.model_validate(plan_dict)
+    with pytest.raises(ValueError, match="topological order"):
+        plan.validate_against(dag)
+
+
+def test_replacement_must_target_leaf(
+    dag_dict: dict, replacement_dict: dict
+) -> None:
+    dag = ProofDAG.model_validate(dag_dict)
+    replacement_dict["target_node_id"] = "n2"
+    replacement = ReplacementSpec.model_validate(replacement_dict)
+    with pytest.raises(ValueError, match="not a DAG leaf"):
+        replacement.validate_against(dag)
+
+
+def test_diffusion_cannot_change_dag_dependencies(
+    dag_dict: dict,
+    plan_dict: dict,
+    diffused_dict: dict,
+) -> None:
+    dag = ProofDAG.model_validate(dag_dict)
+    plan = MethodPlan.model_validate(plan_dict)
+    diffused_dict["node_instantiations"][1]["dependencies"] = []
+    diffused = DiffusedProof.model_validate(diffused_dict)
+    with pytest.raises(ValueError, match="changes dependencies"):
+        diffused.validate_against(dag, plan)