Add test for --debug CLI option

tests/end-to-end/generic/debug.phpt

@@ -0,0 +1,30 @@
+--TEST--
+phpunit --debug ../../_files/BankAccountTest.php
+--FILE--
+<?php declare(strict_types=1);
+$_SERVER['argv'][] = '--do-not-cache-result';
+$_SERVER['argv'][] = '--no-configuration';
+$_SERVER['argv'][] = '--debug';
+$_SERVER['argv'][] = __DIR__ . '/../_files/basic/SuccessTest.php';
+
+require_once __DIR__ . '/../../bootstrap.php';
+
+(new PHPUnit\TextUI\Application)->run($_SERVER['argv']);
+--EXPECTF--
+PHPUnit Started (PHPUnit %s using %s)
+Test Runner Configured
+Test Suite Loaded (1 test)
+Event Facade Sealed
+Test Runner Started
+Test Suite Sorted
+Test Runner Execution Started (1 test)
+Test Suite Started (PHPUnit\TestFixture\Basic\SuccessTest, 1 test)
+Test Preparation Started (PHPUnit\TestFixture\Basic\SuccessTest::testOne)
+Test Prepared (PHPUnit\TestFixture\Basic\SuccessTest::testOne)
+Assertion Succeeded (Constraint: is true, Value: true)
+Test Passed (PHPUnit\TestFixture\Basic\SuccessTest::testOne)
+Test Finished (PHPUnit\TestFixture\Basic\SuccessTest::testOne)
+Test Suite Finished (PHPUnit\TestFixture\Basic\SuccessTest, 1 test)
+Test Runner Execution Finished
+Test Runner Finished
+PHPUnit Finished (Shell Exit Code: 0)