add Messages.delete_all! (#20)

lib/outboxer/messages.rb

@@ -43,5 +43,17 @@ def unpublished!(limit: 1, order: :asc)
           .to_a
       end
     end
+
+    def delete_all!
+      ActiveRecord::Base.connection_pool.with_connection do
+        ActiveRecord::Base.transaction do
+          Models::Frame.delete_all
+          Models::Exception.delete_all
+          Models::Message.delete_all
+        end
+      end
+
+      nil
+    end
   end
 end

spec/lib/outboxer/messages/delete_all_spec.rb

@@ -0,0 +1,33 @@
+require 'spec_helper'
+
+module Outboxer
+  RSpec.describe Messages do
+    describe '.delete_all!' do
+      let!(:message_1) { create(:outboxer_message, :failed) }
+      let!(:exception_1) { create(:outboxer_exception, message: message_1) }
+      let!(:frame_1) { create(:outboxer_frame, exception: exception_1) }
+
+      let!(:message_2) { create(:outboxer_message, :failed) }
+      let!(:exception_2) { create(:outboxer_exception, message: message_2) }
+      let!(:frame) { create(:outboxer_frame, exception: exception_2) }
+
+      let!(:result) { Messages.delete_all! }
+
+      it 'deletes all messages' do
+        expect(Models::Message.count).to eq(0)
+      end
+
+      it 'deletes all exceptions' do
+        expect(Models::Exception.count).to eq(0)
+      end
+
+      it 'deletes all frames' do
+        expect(Models::Frame.count).to eq(0)
+      end
+
+      it 'returns nil' do
+        expect(result).to be_nil
+      end
+    end
+  end
+end