diff --git a/spec/factories/file_type.rb b/spec/factories/file_type.rb
index d1ec9baf..375f9ed7 100644
--- a/spec/factories/file_type.rb
+++ b/spec/factories/file_type.rb
@@ -67,6 +67,13 @@ FactoryGirl.define do
     singleton_file_type
   end
 
+  factory :dot_md, class: FileType do
+    created_by_admin
+    file_extension '.md'
+    name 'Markdown'
+    singleton_file_type
+  end
+
   factory :dot_mp3, class: FileType do
     binary
     created_by_admin
diff --git a/spec/lib/file_tree_spec.rb b/spec/lib/file_tree_spec.rb
new file mode 100644
index 00000000..4e0d3671
--- /dev/null
+++ b/spec/lib/file_tree_spec.rb
@@ -0,0 +1,119 @@
+require 'rails_helper'
+
+describe FileTree do
+  let(:file_tree) { described_class.new }
+
+  describe '#file_icon' do
+    let(:file_icon) { file_tree.send(:file_icon, file) }
+
+    context 'for a media file' do
+      context 'for an audio file' do
+        let(:file) { FactoryGirl.build(:file, file_type: FactoryGirl.build(:dot_mp3)) }
+
+        it 'is an audio file icon' do
+          expect(file_icon).to include('fa-file-audio-o')
+        end
+      end
+
+      context 'for an image file' do
+        let(:file) { FactoryGirl.build(:file, file_type: FactoryGirl.build(:dot_jpg)) }
+
+        it 'is an image file icon' do
+          expect(file_icon).to include('fa-file-image-o')
+        end
+      end
+
+      context 'for a video file' do
+        let(:file) { FactoryGirl.build(:file, file_type: FactoryGirl.build(:dot_mp4)) }
+
+        it 'is a video file icon' do
+          expect(file_icon).to include('fa-file-video-o')
+        end
+      end
+    end
+
+    context 'for other files' do
+      context 'for a read-only file' do
+        let(:file) { FactoryGirl.build(:file, read_only: true) }
+
+        it 'is a lock icon' do
+          expect(file_icon).to include('fa-lock')
+        end
+      end
+
+      context 'for an executable file' do
+        let(:file) { FactoryGirl.build(:file, file_type: FactoryGirl.build(:dot_py)) }
+
+        it 'is a code file icon' do
+          expect(file_icon).to include('fa-file-code-o')
+        end
+      end
+
+      context 'for a renderable file' do
+        let(:file) { FactoryGirl.build(:file, file_type: FactoryGirl.build(:dot_svg)) }
+
+        it 'is a text file icon' do
+          expect(file_icon).to include('fa-file-text-o')
+        end
+      end
+
+      context 'for all other files' do
+        let(:file) { FactoryGirl.build(:file, file_type: FactoryGirl.build(:dot_md)) }
+
+        it 'is a generic file icon' do
+          expect(file_icon).to include('fa-file-o')
+        end
+      end
+    end
+  end
+
+  describe '#folder_icon' do
+    it 'is a folder icon' do
+      expect(file_tree.send(:folder_icon)).to include('fa-folder-o')
+    end
+  end
+
+  describe '#node_icon' do
+    let(:node_icon) { file_tree.send(:node_icon, node) }
+    let(:root) { Tree::TreeNode.new('') }
+
+    context 'for the root node' do
+      let(:node) { root }
+
+      it 'is a folder icon' do
+        expect(node_icon).to eq(file_tree.send(:folder_icon))
+      end
+    end
+
+    context 'for leaf nodes' do
+      let(:node) { root.add(Tree::TreeNode.new('')) }
+
+      it 'is a file icon' do
+        expect(file_tree).to receive(:file_icon)
+        node_icon
+      end
+    end
+
+    context 'for intermediary nodes' do
+      let(:node) do
+        root.add(Tree::TreeNode.new('').tap { |node| node.add(Tree::TreeNode.new('')) })
+      end
+
+      it 'is a folder icon' do
+        expect(node_icon).to eq(file_tree.send(:folder_icon))
+      end
+    end
+  end
+
+  describe '#to_js_tree' do
+    let(:js_tree) { file_tree.to_js_tree }
+
+    it 'returns a String' do
+      expect(js_tree).to be_a(String)
+    end
+
+    it 'produces the required JSON format' do
+      expect(JSON.parse(js_tree).deep_symbolize_keys).to eq(core: {data: file_tree.send(:map_to_js_tree, file_tree)})
+    end
+  end
+end