diff --git a/tests/Core/Ruleset/RegisterSniffsTest.php b/tests/Core/Ruleset/RegisterSniffsTest.php
index 8aa7afc7a0..75adf6e527 100644
--- a/tests/Core/Ruleset/RegisterSniffsTest.php
+++ b/tests/Core/Ruleset/RegisterSniffsTest.php
@@ -41,14 +41,14 @@ final class RegisterSniffsTest extends TestCase
      * @var array<string>
      */
     private static $psr1SniffFiles = [
+        'Generic/Sniffs/Files/ByteOrderMarkSniff.php',
+        'Generic/Sniffs/NamingConventions/UpperCaseConstantNameSniff.php',
+        'Generic/Sniffs/PHP/DisallowAlternativePHPTagsSniff.php',
+        'Generic/Sniffs/PHP/DisallowShortOpenTagSniff.php',
         'PSR1/Sniffs/Classes/ClassDeclarationSniff.php',
         'PSR1/Sniffs/Files/SideEffectsSniff.php',
         'PSR1/Sniffs/Methods/CamelCapsMethodNameSniff.php',
-        'Generic/Sniffs/PHP/DisallowAlternativePHPTagsSniff.php',
-        'Generic/Sniffs/PHP/DisallowShortOpenTagSniff.php',
-        'Generic/Sniffs/Files/ByteOrderMarkSniff.php',
         'Squiz/Sniffs/Classes/ValidClassNameSniff.php',
-        'Generic/Sniffs/NamingConventions/UpperCaseConstantNameSniff.php',
     ];
 
     /**
@@ -72,9 +72,13 @@ public static function initializeConfigAndRuleset()
         $config        = new ConfigDouble(['--standard=PSR1']);
         self::$ruleset = new Ruleset($config);
 
-        // Remember the original value of the Ruleset::$sniff property as the tests may adjust it.
+        // Remember the original value of the Ruleset::$sniff property as the tests adjust it.
         self::$originalSniffs = self::$ruleset->sniffs;
 
+        // Sort the value to make the tests stable as different OSes will read directories
+        // in a different order and the order is not relevant for these tests. Just the values.
+        ksort(self::$originalSniffs);
+
         // Update the sniff file list.
         $standardsDir  = dirname(dirname(dirname(__DIR__))).DIRECTORY_SEPARATOR;
         $standardsDir .= 'src'.DIRECTORY_SEPARATOR.'Standards'.DIRECTORY_SEPARATOR;
@@ -179,14 +183,17 @@ public function testRegisteredSniffsWithExclusions()
         $ruleset = new Ruleset($config);
 
         $expected = [
+            'PHP_CodeSniffer\\Standards\\Generic\\Sniffs\\Files\\ByteOrderMarkSniff',
+            'PHP_CodeSniffer\\Standards\\Generic\\Sniffs\\NamingConventions\\UpperCaseConstantNameSniff',
             'PHP_CodeSniffer\\Standards\\Generic\\Sniffs\\PHP\\DisallowAlternativePHPTagsSniff',
             'PHP_CodeSniffer\\Standards\\Generic\\Sniffs\\PHP\\DisallowShortOpenTagSniff',
-            'PHP_CodeSniffer\\Standards\\Generic\\Sniffs\\Files\\ByteOrderMarkSniff',
             'PHP_CodeSniffer\\Standards\\Squiz\\Sniffs\\Classes\\ValidClassNameSniff',
-            'PHP_CodeSniffer\\Standards\\Generic\\Sniffs\\NamingConventions\\UpperCaseConstantNameSniff',
         ];
 
-        $this->assertSame($expected, array_keys($ruleset->sniffs));
+        $actual = array_keys($ruleset->sniffs);
+        sort($actual);
+
+        $this->assertSame($expected, $actual);
 
     }//end testRegisteredSniffsWithExclusions()
 
@@ -213,8 +220,8 @@ public function testRegisteredSniffsBothRestrictionsAndExclusions()
         ];
 
         $expected = [
-            'PHP_CodeSniffer\\Standards\\PSR1\\Sniffs\\Classes\\ClassDeclarationSniff',
             'PHP_CodeSniffer\\Standards\\Generic\\Sniffs\\PHP\\DisallowShortOpenTagSniff',
+            'PHP_CodeSniffer\\Standards\\PSR1\\Sniffs\\Classes\\ClassDeclarationSniff',
         ];
 
         self::$ruleset->registerSniffs(self::$psr1SniffAbsolutePaths, $restrictions, $exclusions);
@@ -262,7 +269,7 @@ public function testRegisteredSniffsFiltersOutFilePathsWithoutSniffsDir()
         $extraPathsBaseDir = __DIR__.DIRECTORY_SEPARATOR.'Fixtures'.DIRECTORY_SEPARATOR;
         $extraPaths        = [
             'DirectoryExpansion/.hiddenAbove/src/MyStandard/Utils/NotInSniffsDirSniff.php',
-            'DirectoryExpansion/.hiddenAbove/src/MyStandard/Utils/SubDir\NotInSniffsDirSniff.php',
+            'DirectoryExpansion/.hiddenAbove/src/MyStandard/Utils/SubDir/NotInSniffsDirSniff.php',
         ];
         $extraPaths        = self::relativeToAbsoluteSniffFiles($extraPathsBaseDir, $extraPaths);