gistfile1.txt

def save_with_payment(plan, email,coupon_code)
    if valid?

      if coupon_code == 'LAUNCHDAY' || coupon_code = 'launchday'
      customer = Stripe::Customer.create(description: "#{email}", plan: "#{plan}", card: stripe_card_token, coupon: "LAUNCHDAY")
      self.stripe_customer_token = customer.id
      save!
      else
      customer = Stripe::Customer.create(description: "#{email}", plan: "#{plan}", card: stripe_card_token )
      self.stripe_customer_token = customer.id
      save!
      end
    end
  rescue Stripe::InvalidRequestError => e
    logger.error "Stripe error while creating customer: #{e.message}"
    errors.add :base, "There was a problem with your credit card."
    false
  end

subscription_controller.rb

 @coupon = params[:coupon_code][:coupon]

        respond_to do |format|
          if @subscription.save_with_payment(@subscription.plan, @user.email,@coupon) && @user.save

The following condition will always be true, you should fix that if you haven't spotted it yet... The right hand is assigning, which is truthy.

if coupon_code == 'LAUNCHDAY' || coupon_code = 'launchday'