Raise exceptions upon error in group_stage_service

app/interactors/add_group_stage_to_tournament.rb

@@ -7,10 +7,11 @@ class AddGroupStageToTournament
     tournament = context.tournament
     groups = context.groups
     context.fail! unless tournament.stages.empty?
-    if (group_stage = GroupStageService.generate_group_stage(groups))
+    begin
+      group_stage = GroupStageService.generate_group_stage(groups)
       tournament.stages = [group_stage]
       context.tournament = tournament
-    else
+    rescue StandardError
       context.fail!
     end
   end

app/services/group_stage_service.rb

@@ -2,15 +2,13 @@
 
 class GroupStageService
   def self.generate_group_stage(groups)
-    return false if groups.length.zero?
+    raise 'Cannot generate group stage without groups' if groups.length.zero?
 
     average_group_size = (groups.flatten.length.to_f / groups.length.to_f)
-    if (average_group_size % 1).zero?
+    raise 'Groups need to be equal size' unless (average_group_size % 1).zero?
+
     groups = groups.map(&method(:get_group_object_from))
     Stage.new level: -1, groups: groups
-    else
-      false
-    end
   end
 
   def self.get_group_object_from(team_array)

spec/interactors/add_group_stage_to_tournament_interactor_spec.rb

@@ -35,14 +35,26 @@ RSpec.describe AddGroupStageToTournament do
     end
   end
 
-  context 'playoff generation fails' do
+  context 'empty groups' do
     before do
       expect(class_double('GroupStageService').as_stubbed_const(transfer_nested_constants: true))
         .to receive(:generate_group_stage).with(@groups)
-                                          .and_return(false)
+                                          .and_raise('Cannot generate group stage without groups')
     end
 
-    it 'fails' do
+    it 'playoff generation fails' do
+      expect(empty_tournament_context).to be_a_failure
+    end
+  end
+
+  context 'unequal group sizes' do
+    before do
+      expect(class_double('GroupStageService').as_stubbed_const(transfer_nested_constants: true))
+        .to receive(:generate_group_stage).with(@groups)
+                                          .and_raise('Groups need to be equal size')
+    end
+
+    it 'playoff generation fails' do
       expect(empty_tournament_context).to be_a_failure
     end
   end

spec/services/group_stage_service_spec.rb

@@ -23,11 +23,16 @@ RSpec.describe GroupStageService do
       expect(group_stage_teams).to match_array(@groups.flatten)
     end
 
-    it 'returns false when given different sizes of groups' do
+    it 'raises exception when given different sizes of groups' do
       unequal_groups = @groups
       unequal_groups.first.pop
-      group_stage = GroupStageService.generate_group_stage(@groups)
-      expect(group_stage).to eq(false)
+      expect { GroupStageService.generate_group_stage(unequal_groups) }
+        .to raise_exception 'Groups need to be equal size'
+    end
+
+    it 'raises exception when given no groups' do
+      expect { GroupStageService.generate_group_stage([]) }
+        .to raise_exception 'Cannot generate group stage without groups'
     end
   end