Assign key as variable

- With some minor spec adjustments

app/experiments/application_experiment.rb

@@ -43,12 +43,12 @@ class ApplicationExperiment < Gitlab::Experiment
     # Clears the entire cache for a given experiment. Be careful with this
     # since it would reset all resolved variants for the entire experiment.
     def clear(key:)
+      key = hkey(key)[0] # extract only the first part of the key
       pool do |redis|
-        unless %w[hash none].include?(redis.type(hkey(key)[0]))
-          raise ArgumentError, 'invalid call to clear a non-hash cache key'
+        case redis.type(key)
+        when 'hash', 'none' then redis.del(key)
+        else raise ArgumentError, 'invalid call to clear a non-hash cache key'
         end
-
-        redis.del(hkey(key)[0])
       end
     end
 

spec/experiments/application_experiment/cache_spec.rb

@@ -14,7 +14,7 @@ RSpec.describe ApplicationExperiment::Cache do
     shared_state.with { |r| r.del(key_name) }
   end
 
-  it "allows reading, writing and deleting" do
+  it "allows reading, writing and deleting", :aggregate_failures do
     # we test them all together because they are largely interdependent
 
     expect(subject.read(key_field)).to be_nil

spec/experiments/application_experiment_spec.rb

@@ -69,7 +69,7 @@ RSpec.describe ApplicationExperiment do
       expect(subject.variant.name).to eq('control')
     end
 
-    context "when the rollout out to 100%" do
+    context "when rolled out to 100%" do
       it "returns the first variant name" do
         subject.try(:variant1) {}
         subject.try(:variant2) {}