Test: moved serialization spec from Groupie::Group to Groupie

It's more useful to test the entire Groupie can be serialized than just
one.

spec/groupie/group_spec.rb

@@ -1,7 +1,6 @@
 # frozen_string_literal: true
 
 require 'spec_helper'
-require 'yaml'
 
 RSpec.describe Groupie::Group do
   let(:group) { Groupie::Group.new('test') }
@@ -26,12 +25,4 @@
       group.method(:add).should == group.method(:<<)
     end
   end
-
-  it 'can be serialized and loaded through YAML' do
-    group = Groupie::Group.new 'group'
-    group.add %w[buy flowers]
-    loaded_group = YAML.safe_load(group.to_yaml, permitted_classes: [Groupie::Group])
-    loaded_group.add %w[buy candy]
-    loaded_group.count('candy').should == 1
-  end
 end

spec/groupie_spec.rb

@@ -1,6 +1,7 @@
 # frozen_string_literal: true
 
 require 'spec_helper'
+require 'yaml'
 
 RSpec.describe Groupie do
   it 'has a version' do
@@ -279,4 +280,14 @@
       end
     end
   end
+
+  it 'can be serialized and loaded through YAML' do
+    groupie = Groupie.new
+    groupie['one'].add %w[buy flowers]
+    groupie['two'].add %w[buy roses]
+
+    loaded = YAML.unsafe_load(YAML.dump(groupie))
+
+    expect(loaded.classify_text(%w[buy candy])).to eq(groupie.classify_text(%w[buy candy]))
+  end
 end