Merge branch 'v9/contrib' into v9/dev

# Conflicts:
#	src/Umbraco.Web.BackOffice/Controllers/ContentTypeController.cs

tests/Umbraco.Tests.UnitTests/Umbraco.Web.BackOffice/CollectionBuilders/TreeCollectionBuilderTests.cs

@@ -0,0 +1,36 @@
+using System.Linq;
+using NUnit.Framework;
+using Umbraco.Cms.Core.Trees;
+using Umbraco.Cms.Web.BackOffice.Trees;
+
+namespace Umbraco.Cms.Tests.UnitTests.Umbraco.Web.BackOffice.CollectionBuilders
+{
+    public class TreeCollectionBuilderTests
+    {
+        [Test]
+        public void Adding_Tree_To_Collection_Builder()
+        {
+            var collectionBuilder = new TreeCollectionBuilder();
+            var treeDefinition = new Tree(0, "test", "test", "test", "test", TreeUse.Main, typeof(LanguageTreeController), false);
+
+            collectionBuilder.AddTree(treeDefinition);
+            var collection = collectionBuilder.CreateCollection(null);
+
+            Assert.AreEqual(1, collection.Count);
+            Assert.AreEqual(treeDefinition, collection.FirstOrDefault());
+        }
+
+        [Test]
+        public void Remove_Tree_From_Collection_Builder()
+        {
+            var collectionBuilder = new TreeCollectionBuilder();
+            var treeDefinition = new Tree(0, "test", "test", "test", "test", TreeUse.Main, typeof(LanguageTreeController), false);
+
+            collectionBuilder.AddTree(treeDefinition);
+            collectionBuilder.RemoveTreeController<LanguageTreeController>();
+            var collection = collectionBuilder.CreateCollection(null);
+
+            Assert.AreEqual(0, collection.Count);
+        }
+    }
+}