test: add coverage on collaborative editing (#1747)

tests/fixtures/built-in-user1.json

@@ -0,0 +1,5 @@
+{
+  "name": "debug1",
+  "email": "debug1@toeverything.info",
+  "password": "debug1"
+}

tests/fixtures/built-in-user2.json

@@ -0,0 +1,5 @@
+{
+  "name": "debug2",
+  "email": "debug2@toeverything.info",
+  "password": "debug2"
+}