Prefer asserting on the exception rather than the message

protects more against the change

spec/consensus_spec.rb

@@ -13,7 +13,7 @@
   it 'needs a proposal' do
     non_proposal = nil
 
-    expect{Consensus.new(non_proposal)}.to raise_error "Needs a proposal"
+    expect{Consensus.new(non_proposal)}.to raise_error NotProposal
     expect{Consensus.new(@proposal)}.to_not raise_error
   end
 
@@ -60,7 +60,7 @@
 
   it "the introduction phase has a minimum duration " do
     minimum_duration_in_days = 2
-    expect{@consensus.next_phase}.to raise_error "Minimum duration not reached yet"
+    expect{@consensus.next_phase}.to raise_error MinimumDurationNotReached
   end
 
   describe "when introduction phase minimum duration has passed" do
@@ -72,7 +72,7 @@
     end
 
     it "can not go to next phase whith unaccepted questions " do
-      expect{@consensus.next_phase}.to raise_error 'There are unaccepted questions'
+      expect{@consensus.next_phase}.to raise_error UnacceptedQuestions
     end
 
     it "can  go to next phase whith all questions are accepted " do

spec/question_spec.rb

@@ -22,16 +22,16 @@
   describe 'when addressed' do
     it "only could be answered by the addressed person" do
       @question.address :person
-      expect{@question.answer(:other_than_addressed)}.to raise_error 'The question is addressed to another person'
+      expect{@question.answer(:other_than_addressed)}.to raise_error NotAllowed
     end
   end
 
   it "must be answered to be accepted " do
-      expect{@question.accept :questioner}.to raise_error 'Must be answered before' 
+      expect{@question.accept :questioner}.to raise_error Unanswered
   end
 
   it "must be answered to be rejected " do
-      expect{@question.reject :questioner, :any_reason}.to raise_error 'Must be answered before' 
+      expect{@question.reject :questioner, :any_reason}.to raise_error Unanswered
   end
 
   describe 'when answered' do
@@ -46,7 +46,7 @@
     end
 
     it "must be accepted by the questioner" do
-      expect{@question.accept :anybody}.to raise_error 'This action must be made by the questioner'
+      expect{@question.accept :anybody}.to raise_error NotQuestioner
     end
 
     it "can be rejected with a reason" do
@@ -55,7 +55,7 @@
     end
 
     it "must be rejected by the questioner" do
-      expect{@question.reject :anybody, :any_reason}.to raise_error 'This action must be made by the questioner'
+      expect{@question.reject :anybody, :any_reason}.to raise_error NotQuestioner
     end
 
   end