🥗 Tobias: Test issuing Payouts twice doesn't create more `Payment…

…s` (#19)

* 🥗 `Tobias`: Issuing `Payouts` doesn't create additional payouts per beneficiary

I thought that this would actually be a problem, but apparently it's
not! Hooray for tests!

* 🥗✨`Tobias`: `Payout#issue` won't create `Payment` for new `Beneficiary`

This one actually needed adjusting! Turns out, `Payout#issue` would
happily create a new `Payment` for a new `Beneficiary`, which is less
than ideal.

Now we have a guard clause that will prevent `Payout#issue` from making
additional `Payments` when there are already `Payments` present.

app/furniture/tobias/payout.rb

@@ -9,6 +9,8 @@ class Payout < ApplicationRecord
     monetize :amount_cents
 
     def issue
+      return if payments.present?
+
       per_beneficiary_amount = (amount / beneficiaries.count)
       beneficiaries.each do |beneficiary|
         payments.create_with(amount: per_beneficiary_amount).find_or_create_by(beneficiary_id: beneficiary.id)

spec/tobias/payout_spec.rb

@@ -29,5 +29,23 @@
         end
       end
     end
+
+    context "when running twice" do
+      it "does not issue multiple payouts, even when beneficiaries are added" do
+        payout = create(:tobias_payout, amount_cents: 100_00)
+
+        create_list(:tobias_beneficiary, 2, trust: payout.trust)
+
+        payout.issue
+
+        create(:tobias_beneficiary, trust: payout.trust)
+
+        # ActiveRecord appears to be caching the `payout.beneficiaries` results
+        # Reload busts that cache.
+        payout.reload
+
+        expect { payout.issue }.not_to(change(payout.payments, :count))
+      end
+    end
   end
 end