Properly assert that AR has disabled prepared statements

ee/spec/lib/ee/gitlab/database_spec.rb

@@ -61,19 +61,24 @@ RSpec.describe Gitlab::Database do
   end
 
   describe '.disable_prepared_statements' do
-    it 'disables prepared statements' do
-      config = {}
+    around do |example|
+      original_config = ::Gitlab::Database.config
+
+      example.run
 
-      expect(ActiveRecord::Base.configurations).to receive(:[])
-        .with(Rails.env)
-        .and_return(config)
+      ActiveRecord::Base.establish_connection(original_config)
+    end
+
+    it 'disables prepared statements' do
+      ActiveRecord::Base.establish_connection(::Gitlab::Database.config.merge(prepared_statements: true))
+      expect(ActiveRecord::Base.connection.prepared_statements).to eq(true)
 
       expect(ActiveRecord::Base).to receive(:establish_connection)
-        .with({ 'prepared_statements' => false })
+        .with(a_hash_including({ 'prepared_statements' => false })).and_call_original
 
       described_class.disable_prepared_statements
 
-      expect(config['prepared_statements']).to eq(false)
+      expect(ActiveRecord::Base.connection.prepared_statements).to eq(false)
     end
   end