Now that we're only running one version of PHPUnit in CI, upgrade to …

…PHPUnit 11.x

.gitignore

@@ -1,5 +1,5 @@
 .DS_Store
-.phpunit.result.cache
+.phpunit.cache
 .vscode
 composer.lock
 phpcs.xml

composer.json

@@ -20,7 +20,7 @@
     "require-dev": {
         "dealerdirect/phpcodesniffer-composer-installer": "^1.0",
         "phpcompatibility/php-compatibility": "^9.3",
-        "phpunit/phpunit": "^6.5 | ^8.5 | ^9.5 | ^10.0",
+        "phpunit/phpunit": "^11.3",
         "squizlabs/php_codesniffer": "^3.10"
     },
     "autoload": {

phpunit.xml.dist

@@ -1,14 +1,14 @@
-<phpunit
+<?xml version="1.0"?>
+<phpunit xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
     backupGlobals="false"
     bootstrap="vendor/autoload.php"
     colors="true"
-    convertErrorsToExceptions="true"
-    convertNoticesToExceptions="true"
-    convertWarningsToExceptions="true"
-    >
-    <testsuites>
-        <testsuite name="Core">
-            <directory suffix="Test.php">tests/</directory>
-        </testsuite>
-    </testsuites>
+    xsi:noNamespaceSchemaLocation="https://schema.phpunit.de/11.3/phpunit.xsd"
+    cacheDirectory=".phpunit.cache"
+>
+  <testsuites>
+    <testsuite name="Core">
+      <directory suffix="Test.php">tests/</directory>
+    </testsuite>
+  </testsuites>
 </phpunit>

tests/ConstantsTest.php

@@ -1,7 +1,10 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Tests;
 
+use PHPUnit\Framework\Attributes\DataProvider;
 use PHPUnit\Framework\TestCase;
 
 /**
@@ -14,13 +17,12 @@ class ConstantsTest extends TestCase
     /**
      * Ensure that each constant is defined and matches the expected value.
      *
-     * @dataProvider constantsProvider
-     *
      * @param string $constant The name of the constant.
      * @param int    $expected The expected value for the constant.
      *
      * @return void
      */
+    #[DataProvider('constantsProvider')]
     public function testConstantsAreDefined(string $constant, int $expected)
     {
         $this->assertTrue(defined($constant), "Expected the '{$constant}' constant to be defined.");