test: move pytest spec tests into the regression suite

CLAUDE.md

@@ -47,7 +47,7 @@ The library uses a **specification-driven regex parsing** pattern with three lay
 
 ## Testing
 
-- **Unit tests** in `tests/test_specs/` — test individual spec parsers against sample data in `tests/test_specs/data/`
+- **Unit tests** in `tests/test_specs/` — cover only behaviour a regression fixture can't express: auto-detection, missing-flag hints (excluded from serialized output), derived-property logic (`function_name`/`error_location` precedence), and verdict combinations driven by synthetic specs. Anything that's "parse a real log with a registered backend and check the structured output" belongs in the regression suite, not here.
 - **Regression tests** in `tests/regressions/` — data-driven: drop a `.log` and matching `.json` into `tests/regressions/samples/<spec>/` and the test auto-discovers them. The `.json` is the expected CLI JSON output minus the `output` field. Marked with `@pytest.mark.regression`, excluded from default pytest runs.
 
 ## Adding a New Verifier Backend

tests/regressions/samples/pytest/multiple.json

@@ -0,0 +1,76 @@
+{
+  "successful": false,
+  "issues": [
+    {
+      "error_type": "AssertionError",
+      "message": "assert 2048 == 208",
+      "stack_trace": [
+        {
+          "trace_index": 0,
+          "path": "tests/test_ai_models.py",
+          "name": null,
+          "line_idx": 26
+        }
+      ],
+      "severity": "error",
+      "error_location": null
+    },
+    {
+      "error_type": "AssertionError",
+      "message": "assert 0 != 0",
+      "stack_trace": [
+        {
+          "trace_index": 0,
+          "path": "tests/test_esbmc.py",
+          "name": null,
+          "line_idx": 78
+        }
+      ],
+      "severity": "error",
+      "error_location": null
+    },
+    {
+      "error_type": "AssertionError",
+      "message": "assert '[Counterexample]' not in 'esbmc --int...ound (k = 5)'",
+      "stack_trace": [
+        {
+          "trace_index": 0,
+          "path": "tests/test_esbmc.py",
+          "name": null,
+          "line_idx": 85
+        }
+      ],
+      "severity": "error",
+      "error_location": null
+    },
+    {
+      "error_type": "AssertionError",
+      "message": "assert 'Compilation Error' != 'Compilation Error'",
+      "stack_trace": [
+        {
+          "trace_index": 0,
+          "path": "tests/test_esbmc.py",
+          "name": null,
+          "line_idx": 135
+        }
+      ],
+      "severity": "error",
+      "error_location": null
+    },
+    {
+      "error_type": "AssertionError",
+      "message": "Different singleton classes should not share the same instance",
+      "stack_trace": [
+        {
+          "trace_index": 0,
+          "path": "tests/test_singleton.py",
+          "name": null,
+          "line_idx": 45
+        }
+      ],
+      "severity": "error",
+      "error_location": null
+    }
+  ],
+  "duration": 0.0
+}

tests/regressions/samples/pytest/multiple_collection_error.json

@@ -0,0 +1,20 @@
+{
+  "successful": false,
+  "issues": [
+    {
+      "error_type": "SyntaxError",
+      "message": "'(' was never closed",
+      "stack_trace": [
+        {
+          "trace_index": 0,
+          "path": "../../.local/share/hatch/env/virtual/esbmc-ai/9ZN5XdZG/hatch-test.py3.12/lib/python3.12/site-packages/_pytest/python.py",
+          "name": "importtestmodule",
+          "line_idx": 497
+        }
+      ],
+      "severity": "error",
+      "error_location": null
+    }
+  ],
+  "duration": 0.0
+}

tests/regressions/samples/pytest/successful.json

@@ -0,0 +1,5 @@
+{
+  "successful": true,
+  "issues": [],
+  "duration": 0.0
+}