Add a set of tests to the in memory fake filesystem

To ensure this continues to work as expected add some
basic functional tests that ensure the existing operations
work (and continue to work).

Change-Id: I2903bf29a77936d850d667d1fbff179a14a57adb

taskflow/tests/unit/persistence/test_memory_persistence.py

@@ -16,6 +16,7 @@
 
 import contextlib
 
+from taskflow import exceptions as exc
 from taskflow.persistence import backends
 from taskflow.persistence.backends import impl_memory
 from taskflow import test
@@ -45,3 +46,64 @@ class MemoryPersistenceTest(test.TestCase, base.PersistenceTestMixin):
         conf = {'connection': 'memory'}  # note no colon
         with contextlib.closing(backends.fetch(conf)) as be:
             self.assertIsInstance(be, impl_memory.MemoryBackend)
+
+
+class MemoryFilesystemTest(test.TestCase):
+
+    @staticmethod
+    def _get_item_path(fs, path):
+        # TODO(harlowja): is there a better way to do this??
+        return fs[path]
+
+    @staticmethod
+    def _del_item_path(fs, path):
+        # TODO(harlowja): is there a better way to do this??
+        del fs[path]
+
+    def test_set_get_ls(self):
+        fs = impl_memory.FakeFilesystem()
+        fs['/d'] = 'd'
+        fs['/c'] = 'c'
+        fs['/d/b'] = 'db'
+        self.assertEqual(2, len(fs.ls('/')))
+        self.assertEqual(1, len(fs.ls('/d')))
+        self.assertEqual('d', fs['/d'])
+        self.assertEqual('c', fs['/c'])
+        self.assertEqual('db', fs['/d/b'])
+
+    def test_ensure_path(self):
+        fs = impl_memory.FakeFilesystem()
+        pieces = ['a', 'b', 'c']
+        path = "/" + "/".join(pieces)
+        fs.ensure_path(path)
+        path = fs.root_path
+        for i, p in enumerate(pieces):
+            if i == 0:
+                path += p
+            else:
+                path += "/" + p
+            self.assertIsNone(fs[path])
+
+    def test_not_found(self):
+        fs = impl_memory.FakeFilesystem()
+        self.assertRaises(exc.NotFound, self._get_item_path, fs, '/c')
+
+    def test_del_root_not_allowed(self):
+        fs = impl_memory.FakeFilesystem()
+        self.assertRaises(ValueError, self._del_item_path, fs, '/')
+
+    def test_link_loop_raises(self):
+        fs = impl_memory.FakeFilesystem()
+        fs['/b'] = 'c'
+        fs.symlink('/b', '/b')
+        self.assertRaises(ValueError, self._get_item_path, fs, '/b')
+
+    def test_ensure_linked_delete(self):
+        fs = impl_memory.FakeFilesystem()
+        fs['/b'] = 'd'
+        fs.symlink('/b', '/c')
+        self.assertEqual('d', fs['/b'])
+        self.assertEqual('d', fs['/c'])
+        del fs['/b']
+        self.assertRaises(exc.NotFound, self._get_item_path, fs, '/c')
+        self.assertRaises(exc.NotFound, self._get_item_path, fs, '/b')