1 files changed, 138 insertions, 0 deletions
diff --git a/tests/test_kernel_models.py b/tests/test_kernel_models.py
new file mode 100644
index 0000000..864d6d5
--- /dev/null
+++ b/tests/test_kernel_models.py
@@ -0,0 +1,138 @@
+from __future__ import annotations
+
+import pytest
+
+from gap_pipeline.kernel_models import (
+    DiffusedProof,
+    JudgeVerdict,
+    MethodPlan,
+    ProofDAG,
+    RenderedVariant,
+    ReplacementPlan,
+)
+
+
+def branched_dag() -> ProofDAG:
+    return ProofDAG.model_validate(
+        {
+            "nodes": [
+                {"node_id": "n1", "claim": "first fact", "dependencies": []},
+                {"node_id": "n2", "claim": "left branch", "dependencies": ["n1"]},
+                {"node_id": "n3", "claim": "right branch", "dependencies": ["n1"]},
+                {
+                    "node_id": "n4",
+                    "claim": "combine branches",
+                    "dependencies": ["n2", "n3"],
+                },
+            ],
+            "terminal_node_id": "n4",
+        }
+    )
+
+
+def test_proof_dag_supports_real_branching() -> None:
+    dag = branched_dag()
+    assert dag.nodes[-1].dependencies == ["n2", "n3"]
+
+
+def test_replacement_must_reference_a_real_dag_node() -> None:
+    replacements = ReplacementPlan.model_validate(
+        {
+            "changes": [
+                {
+                    "slot_id": "s1",
+                    "source_node_id": "n9",
+                    "description": "constant",
+                    "original_value": "1",
+                    "replacement_value": "2",
+                    "guard_condition": "positive",
+                    "guard_justification": "2 is positive",
+                }
+            ],
+            "closure_statement": "No undeclared changes.",
+        }
+    )
+    with pytest.raises(ValueError, match="unknown nodes"):
+        replacements.validate_against(branched_dag())
+
+
+def test_diffusion_preserves_dependencies_and_methods() -> None:
+    dag = branched_dag()
+    methods = MethodPlan.model_validate(
+        {
+            "nodes": [
+                {"node_id": node.node_id, "method_label": f"method {node.node_id}"}
+                for node in dag.nodes
+            ]
+        }
+    )
+    diffused = DiffusedProof.model_validate(
+        {
+            "nodes": [
+                {
+                    "node_id": node.node_id,
+                    "dependencies": node.dependencies,
+                    "method_label": f"method {node.node_id}",
+                    "instantiated_claim": f"new {node.claim}",
+                    "justification": "valid re-instantiation",
+                }
+                for node in dag.nodes
+            ],
+            "terminal_node_id": "n4",
+            "terminal_answer": "answer",
+        }
+    )
+    assert diffused.validate_against(dag, methods) is diffused
+
+    broken = diffused.model_copy(deep=True)
+    broken.nodes[-1].dependencies = ["n3"]
+    with pytest.raises(ValueError, match="dependencies changed"):
+        broken.validate_against(dag, methods)
+
+
+def test_rendered_solution_must_expose_every_node() -> None:
+    dag = branched_dag()
+    methods = MethodPlan.model_validate(
+        {
+            "nodes": [
+                {"node_id": node.node_id, "method_label": f"method {node.node_id}"}
+                for node in dag.nodes
+            ]
+        }
+    )
+    diffused = DiffusedProof.model_validate(
+        {
+            "nodes": [
+                {
+                    "node_id": node.node_id,
+                    "dependencies": node.dependencies,
+                    "method_label": f"method {node.node_id}",
+                    "instantiated_claim": f"new {node.claim}",
+                    "justification": "valid",
+                }
+                for node in dag.nodes
+            ],
+            "terminal_node_id": "n4",
+            "terminal_answer": "answer",
+        }
+    ).validate_against(dag, methods)
+    variant = RenderedVariant(
+        question="New problem",
+        solution="[n1] first [n2] left [n3] right",
+        node_order=dag.node_ids(),
+        terminal_answer="answer",
+    )
+    with pytest.raises(ValueError, match="missing node markers.*n4"):
+        variant.validate_against(dag, diffused)
+
+
+def test_accept_verdict_normalizes_explicit_none_sentinel() -> None:
+    verdict = JudgeVerdict(
+        verdict="accept",
+        step_by_step_check="n1 valid",
+        replacement_check="s1 valid",
+        blocking_issues="None detected.",
+        patch_suggestion="N/A",
+    )
+    assert verdict.blocking_issues == ""
+    assert verdict.patch_suggestion == ""