Add test_rock_path.py

tests/unit/test_rock_path.py

@@ -0,0 +1,24 @@
+# Copyright 2023 Canonical Ltd.
+# See LICENSE file for licensing details.
+import functools
+import pathlib
+
+import rock
+
+_Path = functools.partial(rock._Path, container_=None)
+
+
+def test_path_joining():
+    assert _Path("/foo") == _Path("/foo")
+    assert _Path("/foo") / "bar" == _Path("/foo/bar")
+    assert "/etc" / _Path("foo") / "bar" == _Path("/etc/foo/bar")
+    assert "/etc" / _Path("foo") / "bar" / "baz" == _Path("/etc/foo/bar/baz")
+    assert _Path("/etc", "foo", "bar", "baz") == _Path("/etc/foo/bar/baz")
+    assert _Path("foo") == _Path("foo")
+    assert "etc" / _Path("foo") / "bar" / "baz" == _Path("etc/foo/bar/baz")
+
+
+def test_relative_to_container():
+    assert _Path("/foo").relative_to_container == pathlib.PurePath("/foo")
+    assert _Path("/foo/bar").relative_to_container == pathlib.PurePath("/foo/bar")
+    assert _Path("baz").relative_to_container == pathlib.PurePath("baz")