diff --git a/scripts/dev_test.py b/scripts/dev_test.py
new file mode 100755
index 0000000..7d559e9
--- /dev/null
+++ b/scripts/dev_test.py
@@ -0,0 +1,191 @@
+#!/usr/bin/env python3
+"""Manual two-user dev test.
+
+Sets up a fresh multi-user instance with dave + brut, extracts their
+activities, then hands off to `bincio dev` so you can browse the site.
+
+Run from the project root:
+
+    uv run python scripts/dev_test.py
+
+Options:
+    --fresh    Wipe DATA_DIR before starting (default: reuse if it exists)
+    --no-dev   Stop after extract (skip `bincio dev`)
+
+Credentials:  dave / testpass  and  brut / testpass
+URL:          http://localhost:4321
+"""
+
+import argparse
+import shutil
+import subprocess
+import sys
+from pathlib import Path
+
+PROJECT_DIR = Path(__file__).resolve().parent.parent
+DATA_DIR    = Path("/tmp/bincio_dev_test")
+DAVE_INPUT  = PROJECT_DIR / "tests" / "data" / "dave"
+BRUT_INPUT  = PROJECT_DIR / "tests" / "data" / "brut"
+PASSWORD    = "testpass"
+
+
+def section(msg: str) -> None:
+    print(f"\n\033[1;36m▸ {msg}\033[0m")
+
+
+def ok(msg: str) -> None:
+    print(f"  \033[32m✓\033[0m  {msg}")
+
+
+def warn(msg: str) -> None:
+    print(f"  \033[33m·\033[0m  {msg}")
+
+
+# ── 1. Init instance (dave = admin) ──────────────────────────────────────────
+
+def init_instance() -> None:
+    section("Initialising instance")
+    from bincio.serve.db import create_user, get_user, open_db
+
+    DATA_DIR.mkdir(parents=True, exist_ok=True)
+
+    db = open_db(DATA_DIR)
+    ok("instance.db ready")
+
+    if get_user(db, "dave"):
+        warn("user 'dave' already exists — skipping")
+    else:
+        create_user(db, "dave", "Dave", PASSWORD, is_admin=True)
+        ok("admin user 'dave' created")
+
+    if get_user(db, "brut"):
+        warn("user 'brut' already exists — skipping")
+    else:
+        create_user(db, "brut", "Brut", PASSWORD, is_admin=False)
+        ok("user 'brut' created")
+
+    for handle in ("dave", "brut"):
+        user_dir = DATA_DIR / handle
+        (user_dir / "activities").mkdir(parents=True, exist_ok=True)
+        (user_dir / "edits").mkdir(parents=True, exist_ok=True)
+
+    import json
+    from datetime import datetime, timezone
+    root_index = DATA_DIR / "index.json"
+    if not root_index.exists():
+        root_index.write_text(json.dumps({
+            "bas_version": "1.0",
+            "instance": {"name": "Dev Test", "private": True},
+            "generated_at": datetime.now(timezone.utc).isoformat(),
+            "shards": [
+                {"handle": "dave", "url": "dave/index.json"},
+                {"handle": "brut", "url": "brut/index.json"},
+            ],
+            "activities": [],
+        }, indent=2))
+        ok("root index.json written")
+    else:
+        warn("root index.json already exists — skipping")
+
+
+# ── 2. Extract activities ─────────────────────────────────────────────────────
+
+def extract_user(handle: str, input_dir: Path) -> None:
+    section(f"Extracting activities for {handle}")
+    if not input_dir.exists():
+        print(f"  \033[31m✗\033[0m  Input dir not found: {input_dir}", file=sys.stderr)
+        sys.exit(1)
+
+    cfg_path = DATA_DIR / f"_cfg_{handle}.yaml"
+    cfg_path.write_text(
+        f"owner:\n  handle: {handle}\n"
+        f"input:\n  dirs:\n    - {input_dir}\n"
+        f"output:\n  dir: {DATA_DIR}\n"
+    )
+
+    from click.testing import CliRunner
+    from bincio.extract.cli import extract as extract_cmd
+    result = CliRunner().invoke(extract_cmd, ["--config", str(cfg_path)])
+
+    if result.exit_code != 0:
+        print(f"  \033[31m✗\033[0m  Extract failed:\n{result.output}", file=sys.stderr)
+        if result.exception:
+            import traceback
+            traceback.print_exception(type(result.exception), result.exception,
+                                      result.exception.__traceback__, file=sys.stderr)
+        sys.exit(1)
+
+    acts = list((DATA_DIR / handle / "activities").glob("*.json"))
+    ok(f"{len(acts)} activities extracted → {DATA_DIR / handle / 'activities'}")
+
+
+# ── 3. Merge + manifest ───────────────────────────────────────────────────────
+
+def prepare_serve() -> None:
+    section("Merging sidecars + writing root manifest")
+    from bincio.render.merge import merge_all
+    from bincio.render.cli import _write_root_manifest
+    import bincio.render.cli as render_cli
+    from rich.console import Console
+    render_cli.console = Console()  # normal output
+
+    for handle in ("dave", "brut"):
+        n = merge_all(DATA_DIR / handle)
+        ok(f"{handle}: {n} sidecar(s) merged")
+
+    _write_root_manifest(DATA_DIR)
+    ok("root manifest updated")
+
+
+# ── 4. Hand off to bincio dev ─────────────────────────────────────────────────
+
+def start_dev() -> None:
+    section("Starting bincio dev")
+    print()
+    print("  \033[1mCredentials\033[0m")
+    print(f"    dave  /  {PASSWORD}  (admin)")
+    print(f"    brut  /  {PASSWORD}")
+    print()
+    print("  \033[1mURL\033[0m  http://localhost:4321")
+    print()
+    print("  Press Ctrl+C to stop.\n")
+
+    try:
+        subprocess.run(
+            ["uv", "run", "bincio", "dev", "--data-dir", str(DATA_DIR)],
+            cwd=PROJECT_DIR,
+        )
+    except KeyboardInterrupt:
+        pass
+
+
+# ── main ──────────────────────────────────────────────────────────────────────
+
+def main() -> None:
+    parser = argparse.ArgumentParser(description=__doc__,
+                                     formatter_class=argparse.RawDescriptionHelpFormatter)
+    parser.add_argument("--fresh",  action="store_true", help="Wipe DATA_DIR before starting")
+    parser.add_argument("--no-dev", action="store_true", help="Stop after extract, skip bincio dev")
+    args = parser.parse_args()
+
+    print(f"\033[1mbincio dev test\033[0m  →  {DATA_DIR}")
+
+    if args.fresh and DATA_DIR.exists():
+        section("Wiping existing data dir")
+        shutil.rmtree(DATA_DIR)
+        ok(f"{DATA_DIR} removed")
+
+    init_instance()
+    extract_user("dave", DAVE_INPUT)
+    extract_user("brut", BRUT_INPUT)
+    prepare_serve()
+
+    if not args.no_dev:
+        start_dev()
+    else:
+        print(f"\n\033[32mDone.\033[0m  Data ready at {DATA_DIR}")
+        print(f"Run:  uv run bincio dev --data-dir {DATA_DIR}\n")
+
+
+if __name__ == "__main__":
+    main()
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diff --git a/tests/test_pipeline.py b/tests/test_pipeline.py
new file mode 100644
index 0000000..3e0e87d
--- /dev/null
+++ b/tests/test_pipeline.py
@@ -0,0 +1,123 @@
+"""End-to-end pipeline test: extract → merge → root manifest for two users.
+
+Uses the 20 real FIT files checked into tests/data/dave/ and tests/data/brut/.
+Run with:
+
+    uv run pytest tests/test_pipeline.py -v
+
+Skip during normal CI runs:
+
+    uv run pytest -m "not integration"
+"""
+
+import json
+import tempfile
+from pathlib import Path
+
+import pytest
+from click.testing import CliRunner
+
+from bincio.extract.cli import extract as extract_cmd
+
+TESTS_DIR = Path(__file__).parent
+DATA_DIR = TESTS_DIR / "data"
+DAVE_INPUT = DATA_DIR / "dave"
+BRUT_INPUT = DATA_DIR / "brut"
+
+
+@pytest.fixture(scope="module")
+def data_root():
+    """Run extract for dave and brut into a shared temp dir, yield the data root."""
+    with tempfile.TemporaryDirectory(prefix="bincio_test_") as tmp:
+        root = Path(tmp)
+        runner = CliRunner()
+
+        for handle, input_dir in [("dave", DAVE_INPUT), ("brut", BRUT_INPUT)]:
+            cfg_path = root / f"cfg_{handle}.yaml"
+            cfg_path.write_text(
+                f"owner:\n  handle: {handle}\n"
+                f"input:\n  dirs:\n    - {input_dir}\n"
+                f"output:\n  dir: {root}\n"
+            )
+            result = runner.invoke(extract_cmd, ["--config", str(cfg_path)])
+            assert result.exit_code == 0, (
+                f"bincio extract failed for {handle}:\n{result.output}"
+            )
+
+        yield root
+
+
+@pytest.mark.integration
+@pytest.mark.slow
+class TestPipeline:
+    def test_activities_extracted_dave(self, data_root):
+        acts = list((data_root / "dave" / "activities").glob("*.json"))
+        assert len(acts) >= 8, f"Expected ≥8 activities for dave, got {len(acts)}"
+
+    def test_activities_extracted_brut(self, data_root):
+        acts = list((data_root / "brut" / "activities").glob("*.json"))
+        assert len(acts) >= 8, f"Expected ≥8 activities for brut, got {len(acts)}"
+
+    def test_index_json_dave(self, data_root):
+        index = json.loads((data_root / "dave" / "index.json").read_text())
+        assert len(index["activities"]) >= 8
+        assert index["owner"]["handle"] == "dave"
+
+    def test_index_json_brut(self, data_root):
+        index = json.loads((data_root / "brut" / "index.json").read_text())
+        assert len(index["activities"]) >= 8
+        assert index["owner"]["handle"] == "brut"
+
+    def test_merge_produces_merged_dir(self, data_root):
+        from bincio.render.merge import merge_all
+        merge_all(data_root / "dave")
+        merge_all(data_root / "brut")
+
+        assert (data_root / "dave" / "_merged" / "index.json").exists()
+        assert (data_root / "brut" / "_merged" / "index.json").exists()
+
+    def test_merged_index_has_activities(self, data_root):
+        # Ensure merge ran (idempotent if already done by earlier test in class)
+        from bincio.render.merge import merge_all
+        merge_all(data_root / "dave")
+        merge_all(data_root / "brut")
+
+        for handle in ("dave", "brut"):
+            merged = json.loads((data_root / handle / "_merged" / "index.json").read_text())
+            assert len(merged["activities"]) >= 8, (
+                f"Expected ≥8 merged activities for {handle}"
+            )
+
+    def test_root_manifest(self, data_root):
+        from bincio.render.cli import _user_dirs, _write_root_manifest
+        from rich.console import Console
+
+        # _write_root_manifest uses the module-level console; patch it to suppress output
+        import bincio.render.cli as render_cli
+        render_cli.console = Console(quiet=True)
+
+        _write_root_manifest(data_root)
+
+        manifest = json.loads((data_root / "index.json").read_text())
+        handles = {s["handle"] for s in manifest["shards"]}
+        assert "dave" in handles
+        assert "brut" in handles
+        assert manifest["bas_version"] == "1.0"
+        # Single-user path: no instance.db → private must be False
+        assert manifest["instance"].get("private") is False
+
+    def test_activity_json_structure(self, data_root):
+        """Spot-check that extracted JSON has the required BAS fields."""
+        acts = sorted((data_root / "dave" / "activities").glob("*.json"))
+        detail = json.loads(acts[0].read_text())
+        for field in ("id", "title", "sport", "started_at", "duration_s"):
+            assert field in detail, f"Missing field '{field}' in activity JSON"
+
+    def test_geojson_exists_for_gps_activities(self, data_root):
+        """Each activity with GPS data should have a companion .geojson file."""
+        acts_dir = data_root / "dave" / "activities"
+        json_ids = {p.stem for p in acts_dir.glob("*.json")}
+        geojson_ids = {p.stem for p in acts_dir.glob("*.geojson")}
+        # At least some activities should have tracks (Karoo FIT files always have GPS)
+        assert len(geojson_ids) >= 5, "Expected ≥5 GeoJSON track files for dave"
+        assert geojson_ids.issubset(json_ids), "GeoJSON without matching detail JSON"