WIP exploratory testing of @run[Class]InSeperateProcess annotations

src/Framework/TestCase.php

@@ -686,16 +686,19 @@ public function run(TestResult $result = null): TestResult
             return $result;
         }
 
+        print "## check: TestCase->runInSeperateProcess()\n";
         if ($this->runInSeparateProcess()) {
             $runEntireClass = $this->runClassInSeparateProcess && !$this->runTestInSeparateProcess;
 
             $class = new ReflectionClass($this);
 
             if ($runEntireClass) {
+                print "## @runClassInSeperateProcess\n";
                 $template = new Text_Template(
                     __DIR__ . '/../Util/PHP/Template/TestCaseClass.tpl'
                 );
             } else {
+                print "## @runInSeperateProcess\n";
                 $template = new Text_Template(
                     __DIR__ . '/../Util/PHP/Template/TestCaseMethod.tpl'
                 );

tests/end-to-end/regression/GitHub/3258/Issue3258Test.php

@@ -0,0 +1,38 @@
+<?php
+/*
+ * This file is part of PHPUnit.
+ *
+ * (c) Sebastian Bergmann <sebastian@phpunit.de>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+/**
+ * @preserveGlobalState
+ * @runClassInSeperateProcess
+ */
+class Issue3258Test extends \PHPUnit\Framework\TestCase
+{
+    protected $internalCounter = 0;
+
+    /**
+     */
+    public function testVerifyUntouchedStartStateThenUpdateState()
+    {
+        $this->assertSame(0, $this->internalCounter);
+        $this->assertArrayNotHasKey('Issue3258_test_global', $GLOBALS);
+
+        $this->internalCounter++;
+        $GLOBALS['Issue3258_test_global'] = true;
+    }
+
+    /**
+     * @depends testVerifyUntouchedStartStateThenUpdateState
+     */
+    public function testStateHasBeenKeptBetweenTests()
+    {
+        $this->assertSame(1, $this->internalCounter);
+        $this->assertSame(true, $GLOBALS['Issue3258_test_global']);
+    }
+}