Tighten live-test selection: source-inspection on public getters

The "auto-mark every test that doesn't take requests_mock" heuristic
was overkill — out of 244 collected tests it marked 200, including
every pure unit test of internal helpers (rdb parsing, _to_str, CQL
filter splitting, NWIS_Metadata setters, validation logic, etc).
Marker over-application is cheap on the success path but conveys
the wrong intent and is one more thing to keep in sync.

Refined heuristic: a test is live iff
  (a) it does not take requests_mock as a fixture, AND
  (b) its function-body source references one of the package's public
      user-facing getters (the _PUBLIC_GETTERS set — all `get_*` /
      `what_*` entry points exposed by waterdata, wqp, samples, nadp,
      streamstats, nldi, nwis, and ngwmn modules).

The set is maintained explicitly because there's no programmatic way
for the conftest to know "what counts as a user-facing entry point";
adding a new public getter means adding it here. A regex with `\b`
word boundaries avoids matching internal helpers that happen to
share a prefix (e.g. `_get_args` won't match `get_args`).

Dry-run against the current test inventory:
  - Old heuristic marked: 200 / 244
  - New heuristic marked:  89 / 244
  - Now-unmarked unit tests: 111

Spot-checked the 111 de-marked tests — all are genuinely offline:
rdb_test.py parsers, utils_test.py to_str/BaseMetadata/datetime
helpers, waterdata_filters_test.py CQL-filter logic, nldi_test.py
validators, nwis_test.py metadata setters, etc.

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

Author: thodson-usgs

tests/conftest.py

@@ -1,21 +1,97 @@
 """Auto-retry live-API tests on transient upstream errors.
 
 After PR #273, paginated ``waterdata`` getters propagate mid-walk HTTP
-errors (429 / 5xx / connection drops) instead of silently truncating the
-result. That's the correct behavior for users but makes any CI test that
-hits the live USGS Water Data API susceptible to flaking on a transient
-upstream blip — e.g. the HTTP 502 Bad Gateway that broke CI on PR #273's
-merge to main.
-
-Heuristic: any test that does NOT request the ``requests_mock`` fixture
-is treated as live and gets retried on transient-error patterns only.
-Library bugs raising other exception types still fail on the first try.
+errors (429 / 5xx / connection drops) instead of silently truncating —
+the right behavior, but it makes any CI test that calls the live USGS
+Water Data API susceptible to flaking on a transient upstream blip
+(e.g. the HTTP 502 Bad Gateway that broke CI on PR #273's merge).
+
+Selection: a test is "live" iff (a) it does not request the
+``requests_mock`` fixture, AND (b) its function body references one of
+the package's public user-facing getters (the ``_PUBLIC_GETTERS`` set).
+This skips pure unit tests of internal helpers (``_get_args``,
+``_check_*``, ``_normalize_*``, ``_construct_api_requests``) that
+share the test file with live tests.
+
+Retry: live tests are retried up to twice on a 5-second backoff,
+but only when the failure trace matches a narrow transient-upstream
+pattern. Library bugs raising other exception types still fail on
+the first try.
 """
 
+import inspect
+import re
+
 import pytest
 
-# Anchored loosely — the failure trace embeds the exception message
-# after a long preamble.
+# Public, network-doing entry points. The set is intentionally exhaustive
+# so the source-inspection heuristic catches every test that exercises
+# the library's user-facing API surface. Add new public getters here.
+_PUBLIC_GETTERS = frozenset(
+    {
+        # waterdata
+        "get_channel",
+        "get_combined_metadata",
+        "get_continuous",
+        "get_daily",
+        "get_field_measurements",
+        "get_field_measurements_metadata",
+        "get_latest_continuous",
+        "get_latest_daily",
+        "get_monitoring_locations",
+        "get_nearest_continuous",
+        "get_peaks",
+        "get_ratings",
+        "get_reference_table",
+        "get_time_series_metadata",
+        "get_stats_por",
+        "get_stats_date_range",
+        # wqp / samples
+        "get_results",
+        "get_samples",
+        "get_samples_summary",
+        "what_activities",
+        "what_activity_metrics",
+        "what_detection_limits",
+        "what_habitat_metrics",
+        "what_organizations",
+        "what_project_weights",
+        "what_projects",
+        "what_sites",
+        # nadp
+        "get_annual_MDN_map",
+        "get_annual_NTN_map",
+        "get_zip",
+        # streamstats / nldi
+        "get_basin",
+        "get_features",
+        "get_features_by_data_source",
+        "get_flowlines",
+        "get_sample_watershed",
+        "get_watershed",
+        # nwis (legacy)
+        "get_discharge_measurements",
+        "get_discharge_peaks",
+        "get_dv",
+        "get_gwlevels",
+        "get_info",
+        "get_iv",
+        "get_pmcodes",
+        "get_qwdata",
+        "get_record",
+        "get_stats",
+        "get_water_use",
+        # ngwmn
+        "get_data",
+        "get_levels",
+        "get_sites",
+    }
+)
+
+_PUBLIC_GETTER_RE = re.compile(
+    r"\b(?:" + "|".join(re.escape(n) for n in _PUBLIC_GETTERS) + r")\b"
+)
+
 _TRANSIENT_PATTERNS = [
     r"RuntimeError:\s*(?:429|5\d\d):",  # _raise_for_non_200 output
     r"ConnectionError",  # requests/urllib3
@@ -32,6 +108,12 @@ def pytest_collection_modifyitems(config, items):
     for item in items:
         if "requests_mock" in item.fixturenames:
             continue
+        try:
+            src = inspect.getsource(item.function)
+        except (OSError, TypeError):
+            continue
+        if not _PUBLIC_GETTER_RE.search(src):
+            continue
         item.add_marker(
             pytest.mark.flaky(
                 reruns=_MAX_RERUNS,