message: insertCommandAt function
diff: @@ -20,6 +20,16 @@ export default class TestCase {
  return command;
  }
  + @action insertCommandAt(command, index) {
  + if (!command || command.constructor.name !== "Command") {
  + throw new Error(`Expected to receive Command instead received ${command ? command.constructor.name : command}`);
  + } else if (!index || index.constructor.name !== "Number") {
  + throw new Error(`Expected to receive Number instead received ${index ? index.constructor.name : index}`);
  + } else {
  + this.commands.splice(index, 0, command);
  + }
  + }
  +
  @action removeCommand(command) {
  this.commands.remove(command);
  }
  