Request for Consistent Handler Restoration on expectOutputString and expectOutputRegex Failure

[KentarouTakeda]

Dear Sebastian Bergmann,

This pull request addresses an issue where error and exception handlers are not restored properly when expectOutputString or expectOutputRegex assertions fail. Below is a minimal code example to reproduce the behavior:

<?php

namespace Test;

use PHPUnit\Framework\TestCase;

class Test extends TestCase
{
    public $existsOriginalErrorHandler;
    public $existsOriginalExceptionHandler;

    // Assume that the error handler is changed within the test code.
    public function setUp(): void
    {
        $this->existsOriginalErrorHandler = (bool)set_error_handler(fn () => null);
        $this->existsOriginalExceptionHandler = (bool)set_exception_handler(fn () => null);
    }

    // Assume that the error handler changes are reliably restored to their original state in `tearDown()`.
    public function tearDown(): void
    {
        restore_exception_handler();
        restore_error_handler();
    }

    // In PHPUnit, tests typically start with this handler setting.
    public function test1()
    {
        $this->assertTrue($this->existsOriginalErrorHandler);
        $this->assertFalse($this->existsOriginalExceptionHandler);
    }

    public function test2()
    {
        // The same assertions as before will obviously succeed.
        $this->assertTrue($this->existsOriginalErrorHandler);
        $this->assertFalse($this->existsOriginalExceptionHandler);

        // This assertion is intentionally set to fail. This failure leads to:
        $this->expectOutputString('This test will be failed'); // Failure (intentional)
    }

    // The next test starts without `tearDown()` being executed,
    public function test3()
    {
        // The exact same assertions will fail here.
        $this->assertTrue($this->existsOriginalErrorHandler);
        $this->assertFalse($this->existsOriginalExceptionHandler); // Failure (unintentional)
    }
}

Although this may not be a "bug" per se, the inconsistent behavior makes it challenging for some frameworks to avoid PHPUnit's warning messages like "Test code or tested code ..." . It would be greatly appreciated if this issue could be addressed in PHPUnit to ensure consistent handler restoration.

Thank you for considering this request.

Best regards,
Kentaro Takeda

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 92.32%. Comparing base (d475be0) to head (84cf94e).
Report is 154 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #5842      +/-   ##
============================================
+ Coverage     89.28%   92.32%   +3.03%     
+ Complexity     6585     6555      -30     
============================================
  Files           693      699       +6     
  Lines         19937    19774     -163     
============================================
+ Hits          17801    18256     +455     
+ Misses         2136     1518     -618     

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