test: migrate backend suites to pytest with module coverage gate

Split backend tests into unit and integration suites, add isolated fixtures and coverage enforcement, and update CI and test documentation. Cover current authentication, content, notification, payment, media, and admin flows; fix behaviors revealed by the new tests. Validate both suites and the per-module gate against local PostgreSQL.

scripts/check_coverage.py

@@ -0,0 +1,62 @@
+"""Enforce branch-aware coverage for every eligible backend module."""
+
+import argparse
+import json
+from pathlib import Path
+
+
+ROOT = Path(__file__).resolve().parents[1]
+EXCLUDED_NAMES = {"__init__.py", "apps.py"}
+EXCLUDED_CONFIG = {
+    "config/asgi.py",
+    "config/wsgi.py",
+    "config/services/location.py",
+    "config/services/notifications.py",
+    "config/services/zarinpal.py",
+}
+
+
+def eligible_modules():
+    for source in ("apps", "core", "config"):
+        for path in (ROOT / source).rglob("*.py"):
+            relative = path.relative_to(ROOT).as_posix()
+            if path.name in EXCLUDED_NAMES or relative in EXCLUDED_CONFIG:
+                continue
+            if any(part in {"tests", "migrations"} for part in path.parts):
+                continue
+            if relative.startswith("config/settings/"):
+                continue
+            yield relative
+
+
+def main():
+    parser = argparse.ArgumentParser()
+    parser.add_argument("coverage_json", type=Path)
+    parser.add_argument("--minimum", type=float, default=80.0)
+    args = parser.parse_args()
+    report = json.loads(args.coverage_json.read_text(encoding="utf-8"))
+    files = {name.replace("\\", "/"): data for name, data in report["files"].items()}
+    failures = []
+    for module in sorted(eligible_modules()):
+        data = files.get(module)
+        if data is None:
+            failures.append(f"{module}: absent from coverage report")
+            continue
+        summary = data["summary"]
+        total = summary["num_statements"] + summary["num_branches"]
+        if total == 0:
+            continue
+        covered = total - summary["missing_lines"] - summary["missing_branches"]
+        percent = covered * 100 / total
+        print(f"{percent:6.2f}%  {module}")
+        if percent < args.minimum:
+            failures.append(f"{module}: {percent:.2f}% < {args.minimum:.2f}%")
+    if failures:
+        print("Coverage gate failed:")
+        for failure in failures:
+            print(f"  {failure}")
+        raise SystemExit(1)
+
+
+if __name__ == "__main__":
+    main()