Introduce CallForParticipation status mutation methods

Add the #open! and #close! methods to CallForParticipation in order to
provide an easy way of setting the opens_at and closes_at times.

app/models/call_for_participation.rb

@@ -1,5 +1,17 @@
 class CallForParticipation < ActiveRecord::Base
   belongs_to :conference
+
+  def open!
+    self.opens_at = Time.now unless self.opens_at.present?
+    self.closes_at = nil
+    save
+  end
+
+  def close!
+    self.closes_at = Time.now
+    save
+  end
+
   def open?
     self.opens_at.present? and self.opens_at < Time.now
   end

spec/factories/call_for_participations.rb

@@ -1,8 +1,4 @@
 FactoryGirl.define do
   factory :call_for_participation do
-    conference nil
-opens_at "2015-04-20 18:40:43"
-closes_at "2015-04-20 18:40:43"
   end
-
 end

spec/models/call_for_participation_spec.rb

@@ -70,4 +70,34 @@ RSpec.describe CallForParticipation, type: :model do
       expect(cfp.in_progress?).to be false
     end
   end
+
+  describe '#open!' do
+    it 'changes the status of the CFP to open' do
+      expect { cfp.open! }.to change { cfp.open? }.from(false).to(true)
+    end
+
+    it 'does not change the open time of the CFP when it has already been set' do
+      cfp.opens_at = 10.minutes.ago
+      expect { cfp.open! }.to_not change { cfp.opens_at }
+    end
+
+    it 'unsets the close time of the CFP' do
+      cfp.closes_at = 10.minutes.ago
+      expect { cfp.open! }.to change { cfp.closes_at }.to(nil)
+    end
+
+    it 'saves the record' do
+      expect { cfp.open! }.to change { cfp.persisted? }.from(false).to(true)
+    end
+  end
+
+  describe '#close!' do
+    it 'changes the status of the CFP to closed' do
+      expect { cfp.close! }.to change { cfp.closed? }.from(false).to(true)
+    end
+
+    it 'saves the record' do
+      expect { cfp.close! }.to change { cfp.persisted? }.from(false).to(true)
+    end
+  end
 end