Add spec for reported regression

spec/requests/contributions/donations_spec.rb

@@ -87,6 +87,43 @@ RSpec.describe "Donations", type: :request do
           expect(response).to redirect_to("https://btcpay.example.com/i/Q9GBe143HJIkdpZeH4Ftx5")
         end
       end
+
+      describe "amount in sats" do
+        before do
+          expect(BtcpayManager::CreateInvoice).to receive(:call)
+            .with(amount: 0.0001, currency: "BTC", redirect_url: "http://www.example.com/contributions/donations/1/confirm_btcpay")
+            .and_return({
+              "id" => "Q9GBe143HJIkdpZeH4Ftx5",
+              "amount" => "0.0001",
+              "currency" => "BTC",
+              "checkoutLink" => "#{Setting.btcpay_api_url}/i/Q9GBe143HJIkdpZeH4Ftx5",
+              "expirationTime" => 1707908626,
+              "checkout" => { "redirectURL" => "http://www.example.com/contributions/donations/1/confirm_btcpay" }
+            })
+
+          post "/contributions/donations", params: {
+            donation_method: "btcpay", amount: "10000", currency: "sats",
+            public_name: "Garret Holmes"
+          }
+        end
+
+        it "creates a new donation record" do
+          expect(user.donations.count).to eq(1)
+          donation = user.donations.first
+          expect(donation.donation_method).to eq("btcpay")
+          expect(donation.payment_method).to be_nil
+          expect(donation.paid_at).to be_nil
+          expect(donation.public_name).to eq("Garret Holmes")
+          expect(donation.amount_sats).to eq(10000)
+          expect(donation.fiat_amount).to be_nil
+          expect(donation.fiat_currency).to be_nil
+          expect(donation.btcpay_invoice_id).to eq("Q9GBe143HJIkdpZeH4Ftx5")
+        end
+
+        it "redirects to the BTCPay checkout page" do
+          expect(response).to redirect_to("https://btcpay.example.com/i/Q9GBe143HJIkdpZeH4Ftx5")
+        end
+      end
     end
   end