Added regression test for sebastianbergmann#1351.

tests/Regression/GitHub/1351.phpt

@@ -0,0 +1,27 @@
+--TEST--
+GH-1351: Test result does not serialize test class in process isolation
+--FILE--
+<?php
+
+$_SERVER['argv'][1] = '--no-configuration';
+$_SERVER['argv'][2] = '--process-isolation';
+$_SERVER['argv'][3] = 'Issue1351Test';
+$_SERVER['argv'][4] = __DIR__ . '/1351/Issue1351Test.php';
+
+require __DIR__ . '/../../bootstrap.php';
+PHPUnit_TextUI_Command::main();
+?>
+--EXPECTF--
+PHPUnit %s by Sebastian Bergmann.
+
+F.
+
+Time: %s, Memory: %sMb
+
+There was 1 failure:
+
+1) Issue1351Test::testChildProcessDoesNotLeakPre
+Expected failure.
+%A
+FAILURES!
+Tests: 2, Assertions: 3, Failures: 1.

tests/Regression/GitHub/1351/Issue1351Test.php

@@ -0,0 +1,21 @@
+<?php
+class Issue1351Test extends PHPUnit_Framework_TestCase
+{
+    protected $instance;
+
+    /**
+     * @runInSeparateProcess
+     */
+    public function testChildProcessDoesNotLeakPre()
+    {
+        $this->instance = new UserData();
+        $this->assertFalse(TRUE, 'Expected failure.');
+    }
+
+    public function testChildProcessDoesNotLeakPost()
+    {
+        $this->assertNull($this->instance);
+        $this->assertFalse(class_exists('UserData', false), 'Class of child process does not exist.');
+    }
+
+}

tests/Regression/GitHub/1351/UserData.php

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+<?php
+class UserData
+{
+}