Add validate-feed helper script

tests/test_validate_feed_script.py

@@ -0,0 +1,67 @@
+import os
+import stat
+import subprocess
+from pathlib import Path
+
+
+def test_validate_feed_script_changes_to_feedvalidator_and_forwards_args(
+    tmp_path: Path,
+) -> None:
+    script_path = Path(__file__).resolve().parents[1] / "scripts" / "validate-feed"
+    feedvalidator_dir = tmp_path / "feedvalidator"
+    bin_dir = tmp_path / "bin"
+    caller_dir = tmp_path / "caller"
+    feed_path = caller_dir / "path" / "to" / "feed.rss"
+    trace_dir = tmp_path / "trace"
+
+    feedvalidator_dir.mkdir()
+    bin_dir.mkdir()
+    feed_path.parent.mkdir(parents=True)
+    feed_path.write_text("<rss/>", encoding="utf-8")
+    trace_dir.mkdir()
+
+    uv_path = bin_dir / "uv"
+    uv_path.write_text(
+        """#!/bin/sh
+printf '%s\\n' "$PWD" > "$TRACE_DIR/cwd"
+printf '%s\\n' "$@" > "$TRACE_DIR/args"
+printf 'validator output\\n'
+""",
+        encoding="utf-8",
+    )
+    uv_path.chmod(uv_path.stat().st_mode | stat.S_IXUSR)
+
+    pager_path = bin_dir / "pager"
+    pager_path.write_text(
+        """#!/bin/sh
+cat > "$TRACE_DIR/pager-input"
+""",
+        encoding="utf-8",
+    )
+    pager_path.chmod(pager_path.stat().st_mode | stat.S_IXUSR)
+
+    env = os.environ.copy()
+    env["FEEDVALIDATOR_DIR"] = str(feedvalidator_dir)
+    env["PAGER"] = str(pager_path)
+    env["PATH"] = f"{bin_dir}:{env['PATH']}"
+    env["TRACE_DIR"] = str(trace_dir)
+
+    subprocess.run(
+        [str(script_path), "path/to/feed.rss", "--flag"],
+        check=True,
+        env=env,
+        cwd=caller_dir,
+    )
+
+    assert (trace_dir / "cwd").read_text(encoding="utf-8").strip() == str(
+        feedvalidator_dir
+    )
+    assert (trace_dir / "args").read_text(encoding="utf-8").splitlines() == [
+        "run",
+        "validate_feed.py",
+        str(feed_path.resolve()),
+        "--flag",
+    ]
+    assert (trace_dir / "pager-input").read_text(
+        encoding="utf-8"
+    ) == "validator output\n"