add refund and event logic

tests/Unit/Services/FeeCalculationServiceTest.php

@@ -0,0 +1,24 @@
+<?php
+
+namespace Tests\Unit\Services;
+
+use App\Services\FeeCalculationService;
+use App\Services\Fees\FeeRefundCalculatorService;
+use Mockery;
+use Tests\TestCase;
+
+class FeeCalculationServiceTest extends TestCase
+{
+    public function test_calculate_refund_returns_calculator_amount(): void
+    {
+        $calculator = Mockery::mock(FeeRefundCalculatorService::class);
+        $calculator->shouldReceive('calculateRefund')
+            ->once()
+            ->with([], 10)
+            ->andReturn(['refund_amount' => 123.45]);
+
+        $service = new FeeCalculationService($calculator);
+
+        $this->assertSame(123.45, $service->calculateRefund([], 10));
+    }
+}