Write tests and ensure adding instances works

rojo-test/serve-test-snapshots/serve_test__add_folder_all-2.snap

@@ -0,0 +1,26 @@
+---
+source: rojo-test/src/serve_test.rs
+expression: "read_response.intern_and_redact(&mut redactions, root_id)"
+---
+instances:
+  id-2:
+    Id: id-2
+    Parent: ~
+    Name: add_folder
+    ClassName: Folder
+    Properties: {}
+    Children:
+      - id-3
+    Metadata:
+      ignoreUnknownInstances: false
+  id-3:
+    Id: id-3
+    Parent: id-2
+    Name: my-new-folder
+    ClassName: Folder
+    Properties: {}
+    Children: []
+    Metadata:
+      ignoreUnknownInstances: false
+messageCursor: 1
+sessionId: id-1

rojo-test/serve-test-snapshots/serve_test__add_folder_all.snap

@@ -0,0 +1,16 @@
+---
+source: rojo-test/src/serve_test.rs
+expression: "read_response.intern_and_redact(&mut redactions, root_id)"
+---
+instances:
+  id-2:
+    Id: id-2
+    Parent: ~
+    Name: add_folder
+    ClassName: Folder
+    Properties: {}
+    Children: []
+    Metadata:
+      ignoreUnknownInstances: false
+messageCursor: 0
+sessionId: id-1

rojo-test/serve-test-snapshots/serve_test__add_folder_info.snap

@@ -0,0 +1,9 @@
+---
+source: rojo-test/src/serve_test.rs
+expression: redactions.redacted_yaml(info)
+---
+expectedPlaceIds: ~
+protocolVersion: 3
+rootInstanceId: id-2
+serverVersion: 0.6.0-dev
+sessionId: id-1

rojo-test/serve-test-snapshots/serve_test__add_folder_subscribe.snap

@@ -0,0 +1,19 @@
+---
+source: rojo-test/src/serve_test.rs
+expression: "subscribe_response.intern_and_redact(&mut redactions, ())"
+---
+messageCursor: 1
+messages:
+  - removedInstances: []
+    addedInstances:
+      id-3:
+        Id: id-3
+        Parent: id-2
+        Name: my-new-folder
+        ClassName: Folder
+        Properties: {}
+        Children: []
+        Metadata:
+          ignoreUnknownInstances: false
+    updatedInstances: []
+sessionId: id-1