1 files changed, 74 insertions, 0 deletions
diff --git a/hooks/tests/test_common.py b/hooks/tests/test_common.py
new file mode 100644
index 0000000..10e6097
--- /dev/null
+++ b/hooks/tests/test_common.py
@@ -0,0 +1,74 @@
+"""Tests for hooks/_common.py — read_referenced_file and scan_attribution."""
+
+import sys
+from pathlib import Path
+
+HOOKS_DIR = Path(__file__).resolve().parent.parent
+if str(HOOKS_DIR) not in sys.path:
+    sys.path.insert(0, str(HOOKS_DIR))
+
+import _common  # noqa: E402
+
+
+# --- read_referenced_file: normal cases ------------------------------------
+
+def test_read_referenced_file_returns_content(tmp_path):
+    f = tmp_path / "msg.txt"
+    f.write_text("hello world\n")
+    assert _common.read_referenced_file(str(f)) == "hello world\n"
+
+
+def test_read_referenced_file_expands_user(tmp_path, monkeypatch):
+    # Point HOME at tmp_path so ~/msg.txt resolves under it.
+    monkeypatch.setenv("HOME", str(tmp_path))
+    monkeypatch.setattr(Path, "home", lambda: tmp_path, raising=False)
+    f = tmp_path / "msg.txt"
+    f.write_text("tilde body")
+    assert _common.read_referenced_file("~/msg.txt") == "tilde body"
+
+
+# --- read_referenced_file: error / boundary cases --------------------------
+
+def test_read_referenced_file_missing_returns_none(tmp_path):
+    assert _common.read_referenced_file(str(tmp_path / "nope.txt")) is None
+
+
+def test_read_referenced_file_directory_returns_none(tmp_path):
+    # A directory is not a regular file.
+    assert _common.read_referenced_file(str(tmp_path)) is None
+
+
+def test_read_referenced_file_oversized_returns_none(tmp_path):
+    f = tmp_path / "big.txt"
+    f.write_text("x" * 50)
+    assert _common.read_referenced_file(str(f), max_bytes=10) is None
+
+
+def test_read_referenced_file_at_limit_is_read(tmp_path):
+    f = tmp_path / "edge.txt"
+    f.write_text("12345")  # exactly 5 bytes
+    assert _common.read_referenced_file(str(f), max_bytes=5) == "12345"
+
+
+def test_read_referenced_file_invalid_utf8_returns_none(tmp_path):
+    f = tmp_path / "bin.dat"
+    f.write_bytes(b"\xff\xfe\x00bad")
+    assert _common.read_referenced_file(str(f)) is None
+
+
+def test_read_referenced_file_empty_string_path_returns_none():
+    assert _common.read_referenced_file("") is None
+
+
+# --- scan_attribution sanity (relied on by the file-backed tests) ----------
+
+def test_scan_attribution_catches_coauthor():
+    assert _common.scan_attribution("Co-Authored-By: Claude")
+
+
+def test_scan_attribution_catches_robot_emoji():
+    assert _common.scan_attribution("nice work \U0001F916")
+
+
+def test_scan_attribution_clean_text_empty():
+    assert _common.scan_attribution("fix: tidy up the parser") == []