Don't crash on price set to 0

#340

rails_application/app/controllers/products_controller.rb

@@ -1,4 +1,19 @@
 class ProductsController < ApplicationController
+  class CreateProduct
+    attr_reader :price, :vat_rate, :product_id, :name
+
+    def initialize(price:, vat_rate:, product_id:, name:)
+      @price = price
+      @vat_rate = vat_rate
+      @product_id = product_id
+      @name = name
+    end
+
+    def valid?
+      price.present? && vat_rate.present? && product_id.present? && name.present? && price.to_d > 0 && vat_rate.to_d > 0
+    end
+  end
+
   def index
     @products = Products::Product.all
   end
@@ -16,6 +31,10 @@ def edit
   end
 
   def create
+    is_form_valid = CreateProduct.new(**product_params).valid?
+
+    return head :bad_request unless is_form_valid
+
     ActiveRecord::Base.transaction do
       create_product(params[:product_id], params[:name])
       if params[:price].present?
@@ -101,4 +120,8 @@ def set_product_future_price_cmd(product_id, price, valid_since)
       valid_since: valid_since
     )
   end
+
+  def product_params
+    params.permit(:name, :price, :vat_rate, :product_id).to_h.symbolize_keys.slice(:price, :vat_rate, :product_id, :name)
+  end
 end

rails_application/test/integration/products_test.rb

@@ -45,4 +45,22 @@ def test_happy_path
                    unit: ""
                  )
   end
+
+  def test_does_not_crash_when_setting_products_price_to_0
+    register_customer("Arkency")
+    product_id = SecureRandom.uuid
+
+    get "/products/new"
+    assert_select "h1", "New Product"
+    post "/products",
+         params: {
+           "authenticity_token" => "[FILTERED]",
+           "product_id" => product_id,
+           "name" => "product name",
+           "price": "0",
+           "vat_rate" => "10"
+         }
+
+    assert_response :bad_request
+  end
 end