Implement Testing::MockRemote#execute

lib/producer/core/testing/mock_remote.rb

@@ -5,6 +5,20 @@ module Producer
         def session
           raise 'no session for mock remote!'
         end
+
+        def execute(command)
+          tokens = command.split
+          program = tokens.shift
+
+          case program
+          when 'echo'
+            tokens.join ' '
+          when 'true'
+            ''
+          when 'false'
+            raise RemoteCommandExecutionError
+          end
+        end
       end
     end
   end