refactor: use RSpec helper spec pattern for EmailHeaderHelper

Use type: :helper to include EmailHeaderHelper automatically, making
the spec more idiomatic. Removed verbose anonymous class construction.

Author: mroderick

spec/helpers/email_header_helper_spec.rb

@@ -1,63 +1,58 @@
-RSpec.describe EmailHeaderHelper do
-  subject do
-    Class.new do
-      include EmailHeaderHelper
-      public :mail_args
-    end.new
-  end
+RSpec.describe EmailHeaderHelper, type: :helper do
+  before { EmailHeaderHelper.module_eval { public :mail_args } }
 
   describe '#mail_args' do
     let(:member) { Struct.new(:id, :email).new(1, 'test@example.com') }
 
     it 'returns mail arguments for valid email' do
-      result = subject.mail_args(member, 'Test Subject')
+      result = helper.mail_args(member, 'Test Subject')
       expect(result[:to]).to eq('test@example.com')
       expect(result[:subject]).to eq('Test Subject')
     end
 
     it 'returns nil for nil email' do
       member = Struct.new(:id, :email).new(1, nil)
-      result = subject.mail_args(member, 'Test Subject')
+      result = helper.mail_args(member, 'Test Subject')
       expect(result).to be_nil
     end
 
     it 'returns nil for blank email' do
       member = Struct.new(:id, :email).new(1, '')
-      result = subject.mail_args(member, 'Test Subject')
+      result = helper.mail_args(member, 'Test Subject')
       expect(result).to be_nil
     end
 
     it 'returns nil for invalid email format' do
       member = Struct.new(:id, :email).new(1, 'invalid-email')
-      result = subject.mail_args(member, 'Test Subject')
+      result = helper.mail_args(member, 'Test Subject')
       expect(result).to be_nil
     end
 
     it 'returns nil for email missing @ symbol' do
       member = Struct.new(:id, :email).new(1, 'invalidexample.com')
-      result = subject.mail_args(member, 'Test Subject')
+      result = helper.mail_args(member, 'Test Subject')
       expect(result).to be_nil
     end
 
     it 'returns nil for email missing TLD' do
       member = Struct.new(:id, :email).new(1, 'invalid@example')
-      result = subject.mail_args(member, 'Test Subject')
+      result = helper.mail_args(member, 'Test Subject')
       expect(result).to be_nil
     end
 
     it 'returns mail arguments for valid email with plus addressing' do
       member = Struct.new(:id, :email).new(1, 'user+tag@example.com')
-      result = subject.mail_args(member, 'Test Subject')
+      result = helper.mail_args(member, 'Test Subject')
       expect(result[:to]).to eq('user+tag@example.com')
     end
 
     it 'includes from email when provided' do
-      result = subject.mail_args(member, 'Test Subject', 'custom@codebar.io')
+      result = helper.mail_args(member, 'Test Subject', 'custom@codebar.io')
       expect(result[:from]).to eq('codebar.io <custom@codebar.io>')
     end
 
     it 'includes cc and bcc when provided' do
-      result = subject.mail_args(member, 'Test Subject', 'from@codebar.io', 'cc@codebar.io', 'bcc@codebar.io')
+      result = helper.mail_args(member, 'Test Subject', 'from@codebar.io', 'cc@codebar.io', 'bcc@codebar.io')
       expect(result[:cc]).to eq('cc@codebar.io')
       expect(result[:bcc]).to eq('bcc@codebar.io')
     end