Skip golden-value tests when file absent (CI isolated-install fix)

CI's "Copy tests to isolated location" step runs tests against the
installed package from /private/tmp/tests/, but does NOT copy
benchmarks/ alongside. My parity tests hard-failed with
FileNotFoundError when the golden JSON was not present at the
expected relative path.

Follow the established repo convention for golden-value fixtures:

    if not GOLDEN_PATH.exists():
        pytest.skip("Golden values file not found; run: Rscript ...")

Matches the pattern used by test_csdid_ported.py,
test_chaisemartin_dhaultfoeuille_parity.py, test_survey_real_data.py,
test_survey_estimator_validation.py, and test_linalg_hc2_bm.py.

Parity tests still run as hard gates:
- when invoked from the repo root (local /pre-merge-check,
  /ai-review-local, dev iteration)
- when benchmarks/ is present alongside tests/ in CI jobs

They skip in the isolated-install job where only tests/ is copied.
Net effect matches the shipping convention for all other
R-backed parity suites in this repo.

190 tests pass (unchanged).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: igerber

tests/test_bandwidth_selector.py

@@ -32,6 +32,14 @@
 
 @pytest.fixture(scope="module")
 def golden():
+    """Load R-generated nprobust golden values. Skip if the file is
+    absent (e.g. in CI's isolated-install path where benchmarks/ is
+    not copied alongside tests/)."""
+    if not GOLDEN_PATH.exists():
+        pytest.skip(
+            "Golden values file not found; "
+            "run: Rscript benchmarks/R/generate_nprobust_golden.R"
+        )
     with GOLDEN_PATH.open() as f:
         return json.load(f)
 

tests/test_nprobust_port.py

@@ -141,6 +141,11 @@ def _setup(self):
             / "data"
             / "nprobust_mse_dpi_golden.json"
         )
+        if not golden_path.exists():
+            pytest.skip(
+                "Golden values file not found; "
+                "run: Rscript benchmarks/R/generate_nprobust_golden.R"
+            )
         with golden_path.open() as f:
             golden = json.load(f)
         dgp = golden["dgp1"]