Stub feature flags before specs executes

Feature flags are stubbed as true by default during tests. The stub
creation can occur after spec code has already executed.

This MR stubs all feature flags to true before any spec code can
execute.

spec/controllers/groups/shared_projects_controller_spec.rb

@@ -17,9 +17,9 @@ RSpec.describe Groups::SharedProjectsController do
     ).execute(group)
   end
 
-  let_it_be(:group) { create(:group) }
-  let_it_be(:user) { create(:user) }
-  let_it_be(:shared_project) do
+  let!(:group) { create(:group) }
+  let!(:user) { create(:user) }
+  let!(:shared_project) do
     shared_project = create(:project, namespace: user.namespace)
     share_project(shared_project)
 

spec/spec_helper.rb

@@ -107,7 +107,6 @@ RSpec.configure do |config|
   config.include FixtureHelpers
   config.include NonExistingRecordsHelpers
   config.include GitlabRoutingHelper
-  config.include StubFeatureFlags
   config.include StubExperiments
   config.include StubGitlabCalls
   config.include StubGitlabData
@@ -140,6 +139,8 @@ RSpec.configure do |config|
   config.include SidekiqMiddleware
   config.include StubActionCableConnection, type: :channel
 
+  include StubFeatureFlags
+
   if ENV['CI'] || ENV['RETRIES']
     # This includes the first try, i.e. tests will be run 4 times before failing.
     config.default_retry_count = ENV.fetch('RETRIES', 3).to_i + 1
@@ -158,6 +159,10 @@ RSpec.configure do |config|
 
     # Reload all feature flags definitions
     Feature.register_definitions
+
+    # Enable all features by default for testing
+    # Reset any changes in after hook.
+    stub_all_feature_flags
   end
 
   config.after(:all) do
@@ -176,9 +181,6 @@ RSpec.configure do |config|
 
   config.before do |example|
     if example.metadata.fetch(:stub_feature_flags, true)
-      # Enable all features by default for testing
-      stub_all_feature_flags
-
       # The following can be removed when we remove the staged rollout strategy
       # and we can just enable it using instance wide settings
       # (ie. ApplicationSetting#auto_devops_enabled)
@@ -203,6 +205,8 @@ RSpec.configure do |config|
       stub_feature_flags(file_identifier_hash: false)
 
       allow(Gitlab::GitalyClient).to receive(:can_use_disk?).and_return(enable_rugged)
+    else
+      unstub_all_feature_flags
     end
 
     # Enable Marginalia feature for all specs in the test suite.
@@ -314,6 +318,9 @@ RSpec.configure do |config|
   config.after do
     Fog.unmock! if Fog.mock?
     Gitlab::CurrentSettings.clear_in_memory_application_settings!
+
+    # Reset all feature flag stubs to default for testing
+    stub_all_feature_flags
   end
 
   config.before(:example, :mailer) do

spec/support/helpers/stub_feature_flags.rb

 # frozen_string_literal: true
 
 module StubFeatureFlags
+  def self.included(base)
+    # Extend Feature class with methods that can stub feature flags.
+    Feature.prepend(StubbedFeature)
+  end
+
   class StubFeatureGate
     attr_reader :flipper_id
 
@@ -9,28 +14,14 @@ module StubFeatureFlags
     end
   end
 
+  # Ensure feature flags are stubbed and reset.
   def stub_all_feature_flags
-    adapter = Flipper::Adapters::Memory.new
-    flipper = Flipper.new(adapter)
-
-    allow(Feature).to receive(:flipper).and_return(flipper)
-
-    # All new requested flags are enabled by default
-    allow(Feature).to receive(:enabled?).and_wrap_original do |m, *args|
-      feature_flag = m.call(*args)
-
-      # If feature flag is not persisted we mark the feature flag as enabled
-      # We do `m.call` as we want to validate the execution of method arguments
-      # and a feature flag state if it is not persisted
-      unless Feature.persisted_name?(args.first)
-        # TODO: this is hack to support `promo_feature_available?`
-        # We enable all feature flags by default unless they are `promo_`
-        # Issue: https://gitlab.com/gitlab-org/gitlab/-/issues/218667
-        feature_flag = true unless args.first.to_s.start_with?('promo_')
-      end
+    Feature.stub = true
+    Feature.reset_flipper
+  end
 
-      feature_flag
-    end
+  def unstub_all_feature_flags
+    Feature.stub = false
   end
 
   # Stub Feature flags with `flag_name: true/false`

spec/support/helpers/stubbed_feature.rb

+# frozen_string_literal: true
+
+# Extend the Feature class with the ability to stub feature flags.
+module StubbedFeature
+  extend ActiveSupport::Concern
+
+  class_methods do
+    # Turn stubbed feature flags on or off.
+    def stub=(stub)
+      @stub = stub
+    end
+
+    def stub?
+      @stub.nil? ? true : @stub
+    end
+
+    # Wipe any previously set feature flags.
+    def reset_flipper
+      @flipper = nil
+    end
+
+    # Replace #flipper method with the optional stubbed/unstubbed version.
+    def flipper
+      if stub?
+        @flipper ||= Flipper.new(Flipper::Adapters::Memory.new)
+      else
+        super
+      end
+    end
+
+    # Replace #enabled? method with the optional stubbed/unstubbed version.
+    def enabled?(*args)
+      feature_flag = super(*args)
+      return feature_flag unless stub?
+
+      # If feature flag is not persisted we mark the feature flag as enabled
+      # We do `m.call` as we want to validate the execution of method arguments
+      # and a feature flag state if it is not persisted
+      unless Feature.persisted_name?(args.first)
+        # TODO: this is hack to support `promo_feature_available?`
+        # We enable all feature flags by default unless they are `promo_`
+        # Issue: https://gitlab.com/gitlab-org/gitlab/-/issues/218667
+        feature_flag = true unless args.first.to_s.start_with?('promo_')
+      end
+
+      feature_flag
+    end
+  end
+end

spec/support_specs/helpers/stub_feature_flags_spec.rb

@@ -119,6 +119,42 @@ RSpec.describe StubFeatureFlags do
     end
   end
 
+  describe 'stub timing' do
+    context 'let_it_be variable' do
+      let_it_be(:let_it_be_var) { Feature.enabled?(:any_feature_flag) }
+
+      it { expect(let_it_be_var).to eq true }
+    end
+
+    context 'before_all variable' do
+      before_all do
+        @suite_var = Feature.enabled?(:any_feature_flag)
+      end
+
+      it { expect(@suite_var).to eq true }
+    end
+
+    context 'before(:all) variable' do
+      before(:all) do
+        @suite_var = Feature.enabled?(:any_feature_flag)
+      end
+
+      it { expect(@suite_var).to eq true }
+    end
+
+    context 'with stub_feature_flags meta' do
+      let(:var) { Feature.enabled?(:any_feature_flag) }
+
+      context 'as true', :stub_feature_flags do
+        it { expect(var).to eq true }
+      end
+
+      context 'as false', stub_feature_flags: false do
+        it { expect(var).to eq false }
+      end
+    end
+  end
+
   def actor(actor)
     case actor
     when Array