fix: Resolve PHP linting errors in test files

- Fix whitespace at end of line in docblock
- Move MockErrorHandler to separate file to comply with PSR-1
- Add proper import for MockErrorHandler class

All tests continue to pass and linting errors are resolved.

Author: lucasheriques

test/MockErrorHandler.php

@@ -0,0 +1,31 @@
+<?php
+
+namespace PostHog\Test;
+
+/**
+ * Mock error handler to capture and verify error reporting
+ */
+class MockErrorHandler
+{
+    private $errors = [];
+
+    public function handleError($code, $message)
+    {
+        $this->errors[] = ['code' => $code, 'message' => $message];
+    }
+
+    public function hasError($code)
+    {
+        foreach ($this->errors as $error) {
+            if ($error['code'] === $code) {
+                return true;
+            }
+        }
+        return false;
+    }
+
+    public function getErrors()
+    {
+        return $this->errors;
+    }
+}

test/PayloadSizeLimitFixTest.php

@@ -4,10 +4,11 @@
 
 use PHPUnit\Framework\TestCase;
 use PostHog\Client;
+use PostHog\Test\MockErrorHandler;
 
 /**
  * Test suite for the 32KB payload size limit fix.
- * 
+ *
  * This addresses the critical data loss issue where events exceeding 32KB
  * when batched together were silently dropped instead of being split and sent.
  */
@@ -209,31 +210,3 @@ public function testNormalSizedBatches(): void
         $this->assertEquals(1, $requestCount, "Only one request should be made for normal batch");
     }
 }
-
-/**
- * Mock error handler to capture and verify error reporting
- */
-class MockErrorHandler
-{
-    private $errors = [];
-
-    public function handleError($code, $message)
-    {
-        $this->errors[] = ['code' => $code, 'message' => $message];
-    }
-
-    public function hasError($code)
-    {
-        foreach ($this->errors as $error) {
-            if ($error['code'] === $code) {
-                return true;
-            }
-        }
-        return false;
-    }
-
-    public function getErrors()
-    {
-        return $this->errors;
-    }
-}