Summary

phpunit --testdox does not show previous exception.

Current behavior

(good) Output for phpunit ExampleTest.php without --testdox shows outer and inner exception.
(bad) Output for phpunit --testdox ExampleTest.php shows outer exception, but not the inner (previous) exception.

~/projects/phplib/phpunit-test $ ./vendor/bin/phpunit --testdox ExampleTest.php 
PHPUnit 11.2.1 by Sebastian Bergmann and contributors.

Runtime:       PHP 8.2.15

E                                                                   1 / 1 (100%)

Time: 00:00.008, Memory: 4.00 MB

Example
 ✘ Foo
   │
   │ Exception: Outer
   │
   │ /home/lemonhead/projects/phplib/phpunit-test/ExampleTest.php:10
   │

ERRORS!
Tests: 1, Assertions: 0, Errors: 1.

How to reproduce

mkdir testdir
cd testdir
composer require phpunit/phpunit
nano ExampleTest.php

Put the following php code:

<?php

declare(strict_types=1);

use PHPUnit\Framework\TestCase;

class ExampleTest extends TestCase {

  public function testFoo() {
    throw new \Exception('Outer', previous: new \Exception('Inner'));
  }

}

Run these commands:

./vendor/bin/phpunit ExampleTest.php
./vendor/bin/phpunit --testdox ExampleTest.php

Expected behavior

Output for both commands contains "Exception: Outer" and "Exception: Inner".

Related issues

There are other issues and PRs that deal with showing previous exception in different use cases.
But it seems this was not done yet for testdox.

About my use case

I personally would not mind to run the test without --testdox.
But I am currently using a tool that adds --testdox parameter by default. See https://github.com/ddev/ddev-drupal-contrib/blob/903026a2fef564b1b7b1fb54213ebb669267995b/commands/web/phpunit#L21
For the steps above I isolated the problem to a minimal project with the latest phpunit I get with composer.