Formalize some patterns in cli specs (#28255)

spec/lib/mastodon/cli/upgrade_spec.rb

@@ -4,23 +4,26 @@ require 'rails_helper'
 require 'mastodon/cli/upgrade'
 
 describe Mastodon::CLI::Upgrade do
+  subject { cli.invoke(action, arguments, options) }
+
   let(:cli) { described_class.new }
+  let(:arguments) { [] }
+  let(:options) { {} }
 
   it_behaves_like 'CLI Command'
 
   describe '#storage_schema' do
-    context 'with records that dont need upgrading' do
-      let(:options) { {} }
+    let(:action) { :storage_schema }
 
+    context 'with records that dont need upgrading' do
       before do
         Fabricate(:account)
         Fabricate(:media_attachment)
       end
 
       it 'does not upgrade storage for the attachments' do
-        expect { cli.invoke(:storage_schema, [], options) }.to output(
-          a_string_including('Upgraded storage schema of 0 records')
-        ).to_stdout
+        expect { subject }
+          .to output_results('Upgraded storage schema of 0 records')
       end
     end
   end