Disable caching for all experiments in tests

spec/controllers/projects/issues_controller_spec.rb

@@ -64,11 +64,6 @@ RSpec.describe Projects::IssuesController do
       end
 
       describe 'the null hypothesis experiment', :snowplow do
-        before do
-          # disable experiment caching
-          allow(Gitlab::Experiment::Configuration).to receive(:cache).and_return(nil)
-        end
-
         it 'defines the expected before actions' do
           expect(controller).to use_before_action(:run_null_hypothesis_experiment)
         end

spec/support/gitlab_experiment.rb

+# frozen_string_literal: true
+
+# Disable all caching for experiments in tests.
+Gitlab::Experiment::Configuration.cache = nil