Return an Enumerator from each* methods when no block is given

spec/oga/xml/attribute_spec.rb

@@ -211,5 +211,17 @@ EOF
           .to yield_successive_args(child, parent)
       end
     end
+
+    describe 'without a block' do
+      it 'returns an enumerator' do
+        child  = Oga::XML::Element.new(:name => 'b')
+        parent = Oga::XML::Element.new(:name => 'a', :children => [child])
+        attr   = described_class.new(:name => 'class', :element => child)
+
+        enum = attr.each_ancestor
+        expect(enum).to be_a(Enumerator)
+        expect(enum.to_a).to eq([child, parent])
+      end
+    end
   end
 end

spec/oga/xml/node_set_spec.rb

@@ -63,6 +63,18 @@ describe Oga::XML::NodeSet do
 
       expect(yielded).to eq([n1, n2])
     end
+
+    describe 'without a block' do
+      it 'returns an enumerator' do
+        n1 = Oga::XML::Element.new(:name => 'a')
+        n2 = Oga::XML::Element.new(:name => 'b')
+        set = described_class.new([n1, n2])
+
+        enum = set.each
+        expect(enum).to be_a(Enumerator)
+        expect(enum.to_a).to eq([n1, n2])
+      end
+    end
   end
 
   describe 'Enumerable behaviour' do

spec/oga/xml/node_spec.rb

@@ -289,5 +289,13 @@ describe Oga::XML::Node do
       expect { |b| @child2.each_ancestor(&b) }
         .to yield_successive_args(@child1, @root)
     end
+
+    describe 'without a block' do
+      it 'returns an enumerator' do
+        enum = @child2.each_ancestor
+        expect(enum).to be_a(Enumerator)
+        expect(enum.to_a).to eq([@child1, @root])
+      end
+    end
   end
 end

spec/oga/xml/traversal_spec.rb

@@ -40,5 +40,17 @@ describe Oga::XML::Traversal do
 
       expect(names).to eq(%w{books book2 title2})
     end
+
+    describe 'without a block' do
+      it 'returns an enumerator' do
+        enum = @document.each_node
+        expect(enum).to be_a(Enumerator)
+
+        names = enum.to_a.map do |node| 
+          node.is_a?(Oga::XML::Element) ? node.name : node.text
+        end
+        expect(names).to eq(%w{books book1 title1 Foo book2 title2 Bar})
+      end
+    end
   end
 end