Add some unit tests for hierarchy module

tests/test_hierarchy.py

@@ -0,0 +1,47 @@
+import rbackup.hierarchy as hierarchy
+import unittest
+
+from unittest.mock import MagicMock, patch
+
+class TestHierarchy(unittest.TestCase):
+    def setUp(self):
+        self.patched_os_path = patch('rbackup.hierarchy.os.path')
+        self.mocked_os_path = self.patched_os_path.start()
+
+        self.mocked_os_path.isdir.return_value = True
+
+        self.hier = hierarchy.Hierarchy('/mnt')
+
+    @patch("rbackup.hierarchy.os.path.isdir")
+    def test_non_dir(self, patched_false_isdir):
+        patched_false_isdir.return_value = False
+
+        with self.assertRaises(ValueError):
+            h = hierarchy.Hierarchy('NotADir')
+
+    def test_base_path(self):
+        self.assertEqual(self.hier.base_dir, "/mnt")
+
+    def test_prev_snapshot(self):
+        raise NotImplementedError
+
+    def test_prev_snapshot_link(self):
+        raise NotImplementedError
+
+    def test_curr_snapshot(self):
+        raise NotImplementedError
+
+    def test_boot_dir(self):
+        raise NotImplementedError
+
+    def test_etc_dir(self):
+        raise NotImplementedError
+
+    def test_home_dir(self):
+        raise NotImplementedError
+
+    def test_root_home_dir(self):
+        raise NotImplementedError
+
+    def tearDown(self):
+        self.patched_os_path.stop()