diff --git a/tests/conftest.py b/tests/conftest.py
index 6f819d6..a47b030 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -2,14 +2,31 @@
 
 import json
 import logging
+import os
+import stat
 import subprocess
+import sys
 import time
+import unittest.mock
 import urllib.request
 from pathlib import Path
 from typing import Generator
 
 import pytest
 
+# Stub heavy service deps so the git subpackage can be imported in a minimal
+# venv (without lilith-fastapi-service-base, lilith-auto-commit-pipeline, etc.)
+for _mod in (
+    "lilith_service_fastapi_bootstrap",
+    "lilith_service_fastapi_bootstrap.settings",
+    "auto_commit_service.config",
+    "auto_commit_service.app",
+):
+    if _mod not in sys.modules:
+        sys.modules[_mod] = unittest.mock.MagicMock()
+
+import pytest
+
 logger = logging.getLogger(__name__)
 
 COORDINATOR_URL = "http://localhost:8210"
@@ -140,3 +157,72 @@ def gpu_settings():
         instruct_model_id="ministral-3b-instruct",
         llm_timeout=30.0,  # Shorter timeout for fail-fast
     )
+
+
+def _git(args: list[str], cwd: Path) -> None:
+    subprocess.run(["git"] + args, cwd=cwd, check=True, capture_output=True)
+
+
+@pytest.fixture
+def divergent_repo(tmp_path: Path) -> Path:
+    """Repo whose local branch and origin/main have diverged on bun.lock.
+
+    Layout after setup:
+      local main  — initial commit + local-only commit (edits bun.lock)
+      origin/main — initial commit + remote-only commit (edits bun.lock differently)
+    Fetching makes local 1 ahead, 1 behind with a guaranteed bun.lock conflict on rebase.
+    """
+    bare = tmp_path / "remote.git"
+    local = tmp_path / "local"
+
+    subprocess.run(["git", "init", "--bare", str(bare)], check=True, capture_output=True)
+
+    local.mkdir()
+    _git(["init"], local)
+    _git(["config", "user.email", "test@test.com"], local)
+    _git(["config", "user.name", "Test User"], local)
+    _git(["remote", "add", "origin", str(bare)], local)
+
+    # Shared base commit
+    (local / "bun.lock").write_text("# lockfile v0\n[[packages]]\n")
+    (local / "package.json").write_text('{"name":"test","version":"1.0.0"}\n')
+    _git(["add", "."], local)
+    _git(["commit", "-m", "Initial commit"], local)
+    _git(["push", "-u", "origin", "master"], local)
+
+    # Remote diverges: adds a dep
+    other = tmp_path / "other"
+    subprocess.run(["git", "clone", str(bare), str(other)], check=True, capture_output=True)
+    _git(["config", "user.email", "test@test.com"], other)
+    _git(["config", "user.name", "Test User"], other)
+    (other / "bun.lock").write_text("# lockfile v0\n[[packages]]\nremote-dep = '1.0.0'\n")
+    _git(["add", "bun.lock"], other)
+    _git(["commit", "-m", "remote: add remote-dep"], other)
+    _git(["push", "origin", "master"], other)
+
+    # Local diverges: adds a different dep
+    (local / "bun.lock").write_text("# lockfile v0\n[[packages]]\nlocal-dep = '2.0.0'\n")
+    _git(["add", "bun.lock"], local)
+    _git(["commit", "-m", "local: add local-dep"], local)
+
+    # Fetch so origin/master is known locally (but do NOT pull — we want divergence)
+    _git(["fetch", "origin"], local)
+
+    return local
+
+
+@pytest.fixture
+def fake_bun_binary(tmp_path: Path, monkeypatch: pytest.MonkeyPatch) -> Path:
+    """Install a stub `bun` script on PATH that exits 0 and writes a clean lockfile."""
+    bin_dir = tmp_path / "stub-bin"
+    bin_dir.mkdir()
+    bun = bin_dir / "bun"
+    bun.write_text(
+        "#!/bin/sh\n"
+        # Write a clean lockfile to the cwd so git add succeeds
+        "printf '# lockfile v0\\n[[packages]]\\n' > bun.lock\n"
+        "exit 0\n"
+    )
+    bun.chmod(bun.stat().st_mode | stat.S_IEXEC | stat.S_IXGRP | stat.S_IXOTH)
+    monkeypatch.setenv("PATH", f"{bin_dir}:{os.environ['PATH']}")
+    return bun