message: ability to insert at index
diff: @@ -16,11 +16,15 @@ export default class TestCase {
  this.swapCommands = this.swapCommands.bind(this);
  }
  - @action createCommand() {
  + @action createCommand(index) {
  + if (index !== undefined && index.constructor.name !== "Number") {
  + throw new Error(`Expected to receive Number instead received ${index !== undefined ? index.constructor.name : index}`);
  + } else {
  const command = new Command();
  - this.commands.push(command);
  + index !== undefined ? this.commands.splice(index, 0, command) : this.commands.push(command);
  return command;
  }
  + }
  @action insertCommandAt(command, index) {
  if (!command || command.constructor.name !== "Command") {
  