Ensure only non-root nodes are marked as terminal

lib/rambling/trie/nodes/raw.rb

@@ -11,7 +11,7 @@ class Raw < Rambling::Trie::Nodes::Node
         # @note This method clears the contents of the chars variable.
         def add chars
           if chars.empty?
-            terminal!
+            terminal! unless root?
           else
             add_to_children_tree chars
           end

spec/lib/rambling/trie/container_spec.rb

@@ -34,6 +34,12 @@
       expect(root.children.size).to eq 1
       expect(root.to_a).to eq %w(hello)
     end
+
+    it 'does nothing with empty strings' do
+      add_word container, ''
+      expect(root.children.size).to eq 0
+      expect(root.to_a).to be_empty
+    end
     # rubocop:enable RSpec/MultipleExpectations
   end
 

spec/lib/rambling/trie/nodes/raw_spec.rb

@@ -32,6 +32,22 @@ def assign_letter letter
   end
 
   describe '#add' do
+    context 'when the node has no parent' do
+      before { node.parent = nil }
+
+      context 'when adding an empty string' do
+        before { add_word node, '' }
+
+        it 'does not add new children' do
+          expect(node.children.size).to eq 0
+        end
+
+        it 'does not mark itself as terminal' do
+          expect(node).not_to be_terminal
+        end
+      end
+    end
+
     context 'when the node has no branches' do
       before { add_word node, 'abc' }
 

spec/lib/rambling/trie/stringifyable_spec.rb

@@ -4,14 +4,22 @@
 
 describe Rambling::Trie::Stringifyable do
   describe '#as_word' do
-    let(:node) { Rambling::Trie::Nodes::Raw.new }
+    let(:parent) { Rambling::Trie::Nodes::Raw.new }
+    let(:node) { Rambling::Trie::Nodes::Raw.new nil, parent }
 
     context 'with an empty node' do
       before { add_word node, '' }
 
       it 'returns nil' do
         expect(node.as_word).to be_empty
       end
+
+      context 'with no parent' do
+        let(:parent) { nil }
+        it 'returns nil' do
+          expect(node.as_word).to be_empty
+        end
+      end
     end
 
     context 'with one letter' do