Add test

This partially reverts commit 26e8bf4.

tests/end-to-end/event/_files/custom-error-handler-registered-in-bootstrap-is-not-overwritten-by-phpunit/bootstrap.php

@@ -0,0 +1,19 @@
+<?php declare(strict_types=1);
+/*
+ * 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.
+ */
+namespace PHPUnit\TestFixture\Event\ErrorHandlerIsNotOverwritten;
+
+use function set_error_handler;
+
+set_error_handler(
+    static function (int $errorNumber, string $errorString, string $errorFile, int $errorLine): bool
+    {
+        return true;
+    },
+);

tests/end-to-end/event/_files/custom-error-handler-registered-in-bootstrap-is-not-overwritten-by-phpunit/phpunit.xml

@@ -0,0 +1,11 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<phpunit xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:noNamespaceSchemaLocation="../../../../../phpunit.xsd"
+         bootstrap="bootstrap.php"
+>
+    <testsuites>
+        <testsuite name="default">
+            <directory>tests</directory>
+        </testsuite>
+    </testsuites>
+</phpunit>

tests/end-to-end/event/_files/custom-error-handler-registered-in-bootstrap-is-not-overwritten-by-phpunit/tests/ExampleTest.php

@@ -0,0 +1,23 @@
+<?php declare(strict_types=1);
+/*
+ * 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.
+ */
+namespace PHPUnit\TestFixture\Event\ErrorHandlerIsNotOverwritten;
+
+use function trigger_error;
+use PHPUnit\Framework\TestCase;
+
+final class ExampleTest extends TestCase
+{
+    public function testOne(): void
+    {
+        trigger_error('message', E_USER_DEPRECATED);
+
+        $this->assertTrue(true);
+    }
+}

tests/end-to-end/event/custom-error-handler-registered-in-bootstrap-is-not-overwritten-by-phpunit.phpt

@@ -0,0 +1,45 @@
+--TEST--
+A custom error handler registered in the test suite's bootstrap script using set_error_handler() is not overwritten by PHPUnit by default
+--FILE--
+<?php declare(strict_types=1);
+$traceFile = tempnam(sys_get_temp_dir(), __FILE__);
+
+$_SERVER['argv'][] = '--do-not-cache-result';
+$_SERVER['argv'][] = '--no-configuration';
+$_SERVER['argv'][] = '--no-output';
+$_SERVER['argv'][] = '--log-events-text';
+$_SERVER['argv'][] = $traceFile;
+$_SERVER['argv'][] = '--configuration';
+$_SERVER['argv'][] = __DIR__ . '/_files/custom-error-handler-registered-in-bootstrap-is-not-overwritten-by-phpunit/phpunit.xml';
+
+require __DIR__ . '/../../bootstrap.php';
+
+(new PHPUnit\TextUI\Application)->run($_SERVER['argv']);
+
+print file_get_contents($traceFile);
+
+unlink($traceFile);
+--EXPECTF--
+PHPUnit Started (PHPUnit %s using %s)
+Test Runner Configured
+Bootstrap Finished (%sbootstrap.php)
+Test Suite Loaded (1 test)
+Event Facade Sealed
+Test Runner Started
+Test Suite Sorted
+Test Runner Execution Started (1 test)
+Test Suite Started (%sphpunit.xml, 1 test)
+Test Suite Started (default, 1 test)
+Test Suite Started (PHPUnit\TestFixture\Event\ErrorHandlerIsNotOverwritten\ExampleTest, 1 test)
+Test Preparation Started (PHPUnit\TestFixture\Event\ErrorHandlerIsNotOverwritten\ExampleTest::testOne)
+Test Prepared (PHPUnit\TestFixture\Event\ErrorHandlerIsNotOverwritten\ExampleTest::testOne)
+Test Triggered Deprecation (PHPUnit\TestFixture\Event\ErrorHandlerIsNotOverwritten\ExampleTest::testOne)
+message
+Test Passed (PHPUnit\TestFixture\Event\ErrorHandlerIsNotOverwritten\ExampleTest::testOne)
+Test Finished (PHPUnit\TestFixture\Event\ErrorHandlerIsNotOverwritten\ExampleTest::testOne)
+Test Suite Finished (PHPUnit\TestFixture\Event\ErrorHandlerIsNotOverwritten\ExampleTest, 1 test)
+Test Suite Finished (default, 1 test)
+Test Suite Finished (%sphpunit.xml, 1 test)
+Test Runner Execution Finished
+Test Runner Finished
+PHPUnit Finished (Shell Exit Code: 0)