diff --git a/tests/Core/Ruleset/RuleInclusionTest.php b/tests/Core/Ruleset/RuleInclusionTest.php
index ef3ad83cac..3f6a7180d6 100644
--- a/tests/Core/Ruleset/RuleInclusionTest.php
+++ b/tests/Core/Ruleset/RuleInclusionTest.php
@@ -47,35 +47,37 @@ final class RuleInclusionTest extends TestCase
     /**
      * Initialize the config and ruleset objects based on the `RuleInclusionTest.xml` ruleset file.
      *
-     * @beforeClass
+     * @before
      *
      * @return void
      */
     public static function initializeConfigAndRuleset()
     {
-        $standard       = __DIR__.'/'.basename(__FILE__, '.php').'.xml';
-        self::$standard = $standard;
+        if (self::$standard === '') {
+            $standard       = __DIR__.'/'.basename(__FILE__, '.php').'.xml';
+            self::$standard = $standard;
 
-        // On-the-fly adjust the ruleset test file to be able to test
-        // sniffs included with relative paths.
-        $contents       = file_get_contents($standard);
-        self::$contents = $contents;
+            // On-the-fly adjust the ruleset test file to be able to test
+            // sniffs included with relative paths.
+            $contents       = file_get_contents($standard);
+            self::$contents = $contents;
 
-        $repoRootDir = basename(dirname(dirname(dirname(__DIR__))));
+            $repoRootDir = basename(dirname(dirname(dirname(__DIR__))));
 
-        $newPath = $repoRootDir;
-        if (DIRECTORY_SEPARATOR === '\\') {
-            $newPath = str_replace('\\', '/', $repoRootDir);
-        }
+            $newPath = $repoRootDir;
+            if (DIRECTORY_SEPARATOR === '\\') {
+                $newPath = str_replace('\\', '/', $repoRootDir);
+            }
 
-        $adjusted = str_replace('%path_root_dir%', $newPath, $contents);
+            $adjusted = str_replace('%path_root_dir%', $newPath, $contents);
 
-        if (file_put_contents($standard, $adjusted) === false) {
-            self::markTestSkipped('On the fly ruleset adjustment failed');
-        }
+            if (file_put_contents($standard, $adjusted) === false) {
+                self::markTestSkipped('On the fly ruleset adjustment failed');
+            }
 
-        $config        = new ConfigDouble(["--standard=$standard"]);
-        self::$ruleset = new Ruleset($config);
+            $config        = new ConfigDouble(["--standard=$standard"]);
+            self::$ruleset = new Ruleset($config);
+        }//end if
 
     }//end initializeConfigAndRuleset()
 
@@ -101,7 +103,7 @@ public function resetRuleset()
      */
     public function testHasSniffCodes()
     {
-        $this->assertCount(48, self::$ruleset->sniffCodes);
+        $this->assertCount(49, self::$ruleset->sniffCodes);
 
     }//end testHasSniffCodes()
 
@@ -318,6 +320,10 @@ public static function dataRegisteredSniffCodes()
                 'Generic.Metrics.CyclomaticComplexity',
                 'PHP_CodeSniffer\Standards\Generic\Sniffs\Metrics\CyclomaticComplexitySniff',
             ],
+            [
+                'Squiz.Files.FileExtension',
+                'PHP_CodeSniffer\Standards\Squiz\Sniffs\Files\FileExtensionSniff',
+            ],
             [
                 'Generic.NamingConventions.CamelCapsFunctionName',
                 'PHP_CodeSniffer\Standards\Generic\Sniffs\NamingConventions\CamelCapsFunctionNameSniff',
@@ -468,6 +474,10 @@ public static function dataSettingInvalidPropertiesOnStandardsAndCategoriesSilen
                 'sniffClass'   => 'PHP_CodeSniffer\Standards\PSR12\Sniffs\Operators\OperatorSpacingSniff',
                 'propertyName' => 'setforallincategory',
             ],
+            'Set property for all sniffs in included category directory'     => [
+                'sniffClass'   => 'PHP_CodeSniffer\Standards\Squiz\Sniffs\Files\FileExtensionSniff',
+                'propertyName' => 'setforsquizfilessniffs',
+            ],
         ];
 
     }//end dataSettingInvalidPropertiesOnStandardsAndCategoriesSilentlyFails()
diff --git a/tests/Core/Ruleset/RuleInclusionTest.xml b/tests/Core/Ruleset/RuleInclusionTest.xml
index 8275fe0111..6b5c0a970b 100644
--- a/tests/Core/Ruleset/RuleInclusionTest.xml
+++ b/tests/Core/Ruleset/RuleInclusionTest.xml
@@ -27,6 +27,14 @@
         </properties>
     </rule>
 
+    <!-- Sniff directory include. -->
+    <rule ref="./src/Standards/Squiz/Sniffs/Files/">
+        <properties>
+            <property name="setforsquizfilessniffs" value="true" />
+        </properties>
+    </rule>
+
+    <!-- Sniff file include. -->
     <rule ref="./src/Standards/Generic/Sniffs/Files/LineLengthSniff.php">
         <properties>
             <property name="lineLimit" value="10" />
@@ -39,6 +47,7 @@
         </properties>
     </rule>
 
+    <!-- Ruleset file include. -->
     <rule ref="./RuleInclusionTest-include.xml">
         <!-- Property being set for all sniffs included in this ruleset. -->
         <properties>