private CharSequence getExpectedActionString(InputOutputEventType expectedEventType) {
        if (expectedEventType == InputOutputEventType.HALT) {
            return new HaltEvent().getExpectedActionDescription();
        } else if (expectedEventType == InputOutputEventType.INPUT) {
            return new InputEvent().getExpectedActionDescription();
        } else if (expectedEventType == InputOutputEventType.OUTPUT) {
            return outputWordPredicates.peek().expectedWordString(); //check if peek will cause error from queue being empty.
        } else {
            throw new AssertionError();
        }

    }