Started adding HookHelper and tests but the tests aren't working

modules/opencase_cases/src/Helper/HookHelper.php

@@ -0,0 +1,9 @@
+<?php
+
+namespace Drupal\opencase_cases\Helper;
+
+class HookHelper {
+    public static function onCaseFeeUpdate(\Drupal\opencase_cases\Entity\OCCaseFee $caseFee) {
+        
+    }
+}

tests/src/Unit/HookHelperTest.php

@@ -0,0 +1,16 @@
+<?php declare(strict_types=1);
+use PHPUnit\Framework\TestCase;
+include '../../../modules/opencase_cases/src/Entity/OCCase.php';
+
+final class HookHelperTest extends TestCase
+{
+    public function testOnCaseFeeUpdate(): void
+    {
+        $caseStub = $this->createStub(\Drupal\opencase_cases\Entity\OCCase::class);
+        $caseStub->total_fee = 5;
+        $caseFeeStub = $this->createStub(\Drupal\opencase_cases\Entity\OCCaseFee::class);
+        $caseFeeStub->amount = 10;
+        $caseFeeStub->method('getCase')->will($this->returnValue($caseStub));
+        $this->assertSame(5,5);
+    }     
+}