add withdrawl and deposit to FiatBalance and Balance

spec/policies/fiat_balance_policy_spec.rb

@@ -2,5 +2,43 @@
 require "rails_helper"
 
 RSpec.describe(FiatBalancePolicy, type: :policy) do
-  pending "add some examples to (or delete) #{__FILE__}"
+  describe "::Scope" do
+    context "when user has balances" do
+      it "return only balances from a user" do
+        create(:fiat_balance)
+        create(:fiat_balance)
+
+        user = build(:user)
+        balance = create(:fiat_balance, user: user)
+
+        balances = FiatBalancePolicy::Scope.new(user, FiatBalance).resolve
+
+        expect(balances).to(eq([balance]))
+      end
+    end
+
+    context "when user has not balances" do
+      it "return empty array" do
+        create(:fiat_balance)
+        create(:fiat_balance)
+
+        user = build(:user)
+
+        balances = FiatBalancePolicy::Scope.new(user, FiatBalance).resolve
+
+        expect(balances).to(eq([]))
+      end
+    end
+
+    context "when user is nil" do
+      it "return empty array" do
+        create(:fiat_balance)
+        create(:fiat_balance)
+
+        balances = FiatBalancePolicy::Scope.new(nil, FiatBalance).resolve
+
+        expect(balances).to(eq([]))
+      end
+    end
+  end
 end