Use the custom RoundRobin strategy directly

- This will allow us to remove it from ApplicationExperiment.

app/experiments/members/invite_email_experiment.rb

@@ -7,12 +7,8 @@ module Members
 
     INVITE_TYPE = 'initial_email'
 
-    def rollout_strategy
-      :round_robin
-    end
-
-    def variants
-      %i[avatar permission_info control]
+    def resolve_variant_name
+      Strategy::RoundRobin.new(feature_flag_name, %i[avatar permission_info control]).execute
     end
   end
 end

spec/experiments/members/invite_email_experiment_spec.rb

@@ -3,26 +3,14 @@
 require 'spec_helper'
 
 RSpec.describe Members::InviteEmailExperiment do
-  subject :invite_email do
-    experiment('members/invite_email', actor: double('Member', created_by: double('User', avatar_url: '_avatar_url_')))
-  end
+  subject(:invite_email) { experiment('members/invite_email', **context) }
+
+  let(:context) { { actor: double('Member', created_by: double('User', avatar_url: '_avatar_url_')) } }
 
   before do
     allow(invite_email).to receive(:enabled?).and_return(true)
   end
 
-  describe "#rollout_strategy" do
-    it "resolves to round_robin" do
-      expect(invite_email.rollout_strategy).to eq(:round_robin)
-    end
-  end
-
-  describe "#variants" do
-    it "has all the expected variants" do
-      expect(invite_email.variants).to match(%i[avatar permission_info control])
-    end
-  end
-
   describe "exclusions", :experiment do
     it "excludes when created by is nil" do
       expect(experiment('members/invite_email')).to exclude(actor: double(created_by: nil))
@@ -34,4 +22,27 @@ RSpec.describe Members::InviteEmailExperiment do
       expect(experiment('members/invite_email')).to exclude(actor: member_without_avatar_url)
     end
   end
+
+  describe "variant resolution", :clean_gitlab_redis_shared_state do
+    it "proves out round robin in variant selection", :aggregate_failures do
+      instance_1 = described_class.new('members/invite_email', **context)
+      allow(instance_1).to receive(:enabled?).and_return(true)
+      instance_2 = described_class.new('members/invite_email', **context)
+      allow(instance_2).to receive(:enabled?).and_return(true)
+      instance_3 = described_class.new('members/invite_email', **context)
+      allow(instance_3).to receive(:enabled?).and_return(true)
+
+      instance_1.try { }
+
+      expect(instance_1.variant.name).to eq('permission_info')
+
+      instance_2.try { }
+
+      expect(instance_2.variant.name).to eq('control')
+
+      instance_3.try { }
+
+      expect(instance_3.variant.name).to eq('avatar')
+    end
+  end
 end