我一直致力于添加这个功能的条纹费，它似乎是工作的罚款，但我需要确保由于所涉及的付款的关键性。
这里的目标是只收取候选人处理月，这意味着只有当他们得到了一个月的贡献。例如，如果候选人得到第一个贡献24日2023年11月，该特定付款应收取额外的费用。然而，其余的付款为该月应该是正常的。同样，第一次付款后，2023年12月24日，将收取额外费用。
投稿_表单.rb

puts "starting else block  ----->>#{amount_cents}" 
        applicable_fee = candidate.determine_fee(amount_cents)
        Stripe::Charge.create({
          amount: amount_cents,
          currency: candidate.candidate_country[candidate.country.to_s.to_sym][:currency],
          source: stripe_token,
          application_fee_amount: applicable_fee,
        # application_fee_amount: ((amount_cents * ((candidate.merchant_rate.to_f * 100) + 2.9) / 100) + 25).to_i,
         statement_descriptor_suffix: "#{get_statement_descriptor.to_s.upcase}",
          on_behalf_of: candidate.stripe_gateway_id,
          transfer_data: {
            destination: candidate.stripe_gateway_id,
          },
        }, stripe_version: '2019-12-03',)

candidate.rb

def determine_fee(amount_cents)
    amount = ((amount_cents * ((merchant_rate.to_f * 100) + 2.9) / 100) + 25).to_i
    return amount unless id ==  3954 
    if fee_paid_on["started_date"].nil? || (next_start_date(fee_paid_on["started_date"].to_datetime, true) <= Time.zone.now)
       amount = ((amount_cents * ((merchant_rate.to_f * 100) + 2.9) / 100) + 25 + 799).to_i
      fee_paid_details
    else 
      amount = ((amount_cents * ((merchant_rate.to_f * 100) + 2.9) / 100) + 25).to_i 
      fee_paid_details
    end
    amount
  end 
  
  def next_start_date(start_date, flag = false)
    puts "next start date ----->>#{start_date}"
    return start_date + 1.month if flag 
  
    t = Time.zone.now
    start_date.month != t.month ? Time.zone.parse("#{start_date.day}/#{t.month}/#{t.year}") : start_date + 1.month
  end  
  #only updating start date and setting it as per next month
  def  fee_paid_details 
    started_date =  fee_paid_on["started_date"]
    new_started_date = (next_start_date(started_date.to_datetime) < Time.zone.now ? started_date.to_datetime : next_start_date(started_date.to_datetime)) if started_date
    update_columns(
      fee_paid_on: {
        "started_date" => started_date.nil? ? Time.zone.now : new_started_date,
        "last_paid_on" => Time.zone.now 
      }
    )
  end

我需要两个部门的洞察力：
1.我如何彻底测试这一点？
1.有人能帮我优化代码吗