1 files changed, 82 insertions, 1 deletions
diff --git a/tests/test_models.py b/tests/test_models.py
index 71dc854..d19b536 100644
--- a/tests/test_models.py
+++ b/tests/test_models.py
@@ -3,7 +3,12 @@ from __future__ import annotations
 import pytest
 from pydantic import ValidationError
 
-from gap_pipeline.models import JudgeVerdict, KernelCandidate, KernelPlan
+from gap_pipeline.models import (
+    JudgeVerdict,
+    KernelCandidate,
+    KernelPlan,
+    ProofPlanDAG,
+)
 
 
 def test_valid_plan_and_candidate(plan_dict: dict, candidate_dict: dict) -> None:
@@ -38,3 +43,79 @@ def test_accept_verdict_cannot_report_blocking_issue() -> None:
             step_by_step_check="checked",
             blocking_issues="an error",
         )
+
+
+def test_path_dag_is_derived_from_ordered_plan(plan_dict: dict) -> None:
+    dag = ProofPlanDAG.from_plan(KernelPlan.model_validate(plan_dict))
+    assert [node.node_id for node in dag.nodes] == ["n1", "n2"]
+    assert dag.nodes[0].dependencies == []
+    assert dag.nodes[1].dependencies == ["n1"]
+    assert dag.terminal_node_id == "n2"
+    assert dag.method_labels_payload()[0].startswith("n1: ")
+
+
+def test_dag_rejects_cycle() -> None:
+    with pytest.raises(ValidationError, match="cycle"):
+        ProofPlanDAG.model_validate(
+            {
+                "nodes": [
+                    {
+                        "node_id": "n1",
+                        "method_label": "first",
+                        "dependencies": ["n2"],
+                    },
+                    {
+                        "node_id": "n2",
+                        "method_label": "second",
+                        "dependencies": ["n1"],
+                    },
+                ],
+                "terminal_node_id": "n2",
+            }
+        )
+
+
+def test_path_dag_rejects_skipped_dependency() -> None:
+    with pytest.raises(ValidationError, match="lead to the terminal"):
+        ProofPlanDAG.model_validate(
+            {
+                "nodes": [
+                    {
+                        "node_id": "n1",
+                        "method_label": "first",
+                        "dependencies": [],
+                    },
+                    {
+                        "node_id": "n2",
+                        "method_label": "second",
+                        "dependencies": [],
+                    },
+                ],
+                "terminal_node_id": "n2",
+            }
+        )
+
+
+def test_judge_verdict_requires_every_dag_node(plan_dict: dict) -> None:
+    dag = ProofPlanDAG.from_plan(KernelPlan.model_validate(plan_dict))
+    verdict = JudgeVerdict(
+        verdict="accept",
+        step_by_step_check="n1 is valid; n2 is valid",
+    )
+    assert verdict.validate_coverage(dag) is verdict
+
+    with pytest.raises(ValueError, match="does not cover DAG nodes.*n2"):
+        JudgeVerdict(
+            verdict="accept",
+            step_by_step_check="n1 is valid",
+        ).validate_coverage(dag)
+
+
+def test_dag_labels_must_match_prompt_a_plan(plan_dict: dict) -> None:
+    plan = KernelPlan.model_validate(plan_dict)
+    dag = ProofPlanDAG.from_plan(plan)
+    changed_plan = plan.model_copy(
+        update={"core_steps": ["a different method", plan.core_steps[1]]}
+    )
+    with pytest.raises(ValueError, match="must equal Prompt-A core_steps"):
+        dag.validate_plan(changed_plan)