diff --git a/tests/project/test_fingerprint.py b/tests/project/test_fingerprint.py
@@ -0,0 +1,97 @@
+from __future__ import annotations
+
+import os
+from pathlib import Path
+
+from pythonnative.project.fingerprint import hash_tree
+
+
+def _write_tree(root: Path, files: dict[str, bytes]) -> None:
+    for rel, content in files.items():
+        path = root / rel
+        path.parent.mkdir(parents=True, exist_ok=True)
+        path.write_bytes(content)
+
+
+def test_identical_trees_under_different_roots_hash_equal(tmp_path: Path) -> None:
+    files = {
+        "src/app.py": b"print('hello')\n",
+        "src/util.py": b"HELPER = True\n",
+        "assets/icon.txt": b"icon\n",
+        "readme.txt": b"notes\n",
+        "license.txt": b"license\n",
+    }
+    a = tmp_path / "a"
+    b = tmp_path / "b"
+    _write_tree(a, files)
+    # Different creation order under a different root.
+    _write_tree(b, dict(reversed(list(files.items()))))
+
+    assert hash_tree(a) == hash_tree(b)
+
+
+def test_changing_bytes_or_renaming_changes_hash(tmp_path: Path) -> None:
+    root = tmp_path / "proj"
+    _write_tree(root, {"src/app.py": b"one\n", "src/util.py": b"two\n"})
+    original = hash_tree(root)
+
+    (root / "src" / "app.py").write_bytes(b"changed\n")
+    assert hash_tree(root) != original
+
+    (root / "src" / "app.py").write_bytes(b"one\n")
+    assert hash_tree(root) == original
+
+    (root / "src" / "app.py").rename(root / "src" / "main.py")
+    assert hash_tree(root) != original
+
+
+def test_mtime_change_does_not_change_hash(tmp_path: Path) -> None:
+    root = tmp_path / "proj"
+    target = root / "src" / "app.py"
+    _write_tree(root, {"src/app.py": b"stable\n"})
+    original = hash_tree(root)
+
+    os.utime(target, (1_700_000_000, 1_700_000_000))
+    assert hash_tree(root) == original
+
+
+def test_ignored_paths_do_not_change_hash(tmp_path: Path) -> None:
+    root = tmp_path / "proj"
+    _write_tree(root, {"src/app.py": b"code\n"})
+    original = hash_tree(root)
+
+    _write_tree(
+        root,
+        {
+            "build/out.bin": b"artifact\n",
+            "__pycache__/app.cpython-313.pyc": b"bytecode\n",
+            ".git/HEAD": b"ref: refs/heads/main\n",
+            "src/app.pyc": b"bytecode-file\n",
+            "src/.DS_Store": b"finder\n",
+        },
+    )
+    assert hash_tree(root) == original
+
+    (root / "src" / "extra.py").write_bytes(b"new\n")
+    assert hash_tree(root) != original
+
+
+def test_missing_root_and_empty_directory_share_empty_digest(tmp_path: Path) -> None:
+    missing = tmp_path / "does-not-exist"
+    empty = tmp_path / "empty"
+    empty.mkdir()
+
+    assert hash_tree(missing) == hash_tree(empty)
+
+
+def test_hashing_a_single_file(tmp_path: Path) -> None:
+    file_a = tmp_path / "a.txt"
+    file_b = tmp_path / "other" / "a.txt"
+    file_a.write_bytes(b"same-bytes\n")
+    file_b.parent.mkdir()
+    file_b.write_bytes(b"same-bytes\n")
+
+    assert hash_tree(file_a) == hash_tree(file_b)
+
+    file_b.write_bytes(b"different\n")
+    assert hash_tree(file_a) != hash_tree(file_b)