ci: add strict test evidence gates

scripts/check_coverage_thresholds.py

@@ -0,0 +1,66 @@
+"""Enforce separate line and branch floors from a coverage.py JSON report."""
+
+from __future__ import annotations
+
+import argparse
+import json
+from pathlib import Path
+from typing import Any
+
+
+def validate_coverage(
+    report: dict[str, Any], *, min_line: float, min_branch: float,
+) -> list[str]:
+    """Return human-readable failures for coverage totals below their floors."""
+    totals = report.get("totals")
+    if not isinstance(totals, dict):
+        return ["coverage report is missing the totals object"]
+
+    failures: list[str] = []
+    metrics = (
+        ("line", "percent_statements_covered", min_line),
+        ("branch", "percent_branches_covered", min_branch),
+    )
+    for label, key, minimum in metrics:
+        value = totals.get(key)
+        if not isinstance(value, (int, float)):
+            failures.append(f"coverage report is missing numeric {key}")
+        elif value < minimum:
+            failures.append(
+                f"{label} coverage {value:.2f}% is below the {minimum:.2f}% floor",
+            )
+    return failures
+
+
+def _parser() -> argparse.ArgumentParser:
+    parser = argparse.ArgumentParser(description=__doc__)
+    parser.add_argument("report", type=Path, help="coverage.py JSON report")
+    parser.add_argument("--min-line", type=float, required=True)
+    parser.add_argument("--min-branch", type=float, required=True)
+    return parser
+
+
+def main() -> int:
+    args = _parser().parse_args()
+    report = json.loads(args.report.read_text(encoding="utf-8"))
+    failures = validate_coverage(
+        report,
+        min_line=args.min_line,
+        min_branch=args.min_branch,
+    )
+    if failures:
+        for failure in failures:
+            print(f"coverage gate failed: {failure}")
+        return 1
+
+    totals = report["totals"]
+    print(
+        "coverage gate passed: "
+        f"line={totals['percent_statements_covered']:.2f}% "
+        f"branch={totals['percent_branches_covered']:.2f}%",
+    )
+    return 0
+
+
+if __name__ == "__main__":
+    raise SystemExit(main())