Subtract store credit from total sent to PayBright

Since PayBright doesn't allow us to modify payments before capturing
them like some other payment methods, we need to ensure we send them the
correct amount right away.

lib/solidus_paybright/params_helper.rb

@@ -15,7 +15,7 @@ def build_redirect_params
       params = {
         # mandatory parameters
         "x_account_id" => credentials[:api_key],
-        "x_amount" => order.total.to_money.to_s,
+        "x_amount" => (order.total - order.total_applicable_store_credit).to_money.to_s,
         "x_currency" => order.currency,
         "x_reference" => @payment.id,
         "x_shop_country" => credentials[:shop_country_code],

spec/lib/solidus_paybright/params_helper_spec.rb

@@ -1,8 +1,10 @@
 require "spec_helper"
 
 describe SolidusPaybright::ParamsHelper do
-  let(:payment_method) { create(:paybright_payment_method, preference_source: "paybright_credentials") }
-  let(:payment) { create(:paybright_payment, payment_method: payment_method) }
+  let(:order) { build_stubbed(:order, total: 110, number: "R123456789", email: "user@example.com") }
+  let(:payment_method) { build_stubbed(:paybright_payment_method, preference_source: "paybright_credentials") }
+  let(:payment) { build_stubbed(:paybright_payment, order: order, payment_method: payment_method) }
+
   subject { described_class.new(payment) }
 
   describe "#new" do
@@ -13,14 +15,6 @@
   end
 
   describe "#build_redirect_params" do
-    before do
-      allow_any_instance_of(Spree::Order).to receive_messages(
-        total: 110,
-        number: "R123456789",
-        email: "user@example.com"
-      )
-    end
-
     it "build the correct parameters for the order" do
       params = subject.build_redirect_params
       expect(params["x_account_id"]).to eq("api-key")
@@ -40,5 +34,13 @@
       allow_any_instance_of(Spree::Order).to receive_messages email: ""
       expect(subject.build_redirect_params.key?("x_customer_email")).to be false
     end
+
+    context "order has store credit applied" do
+      before { allow(order).to receive(:total_applicable_store_credit) { 10 } }
+
+      it "subtracts the credit from the total passed to Paybright" do
+        expect(subject.build_redirect_params["x_amount"]).to eq("100.00")
+      end
+    end
   end
 end