Does this hit the mark ?

tests/Core/Ruleset/ExpandRulesetReferenceTest.php

@@ -0,0 +1,60 @@
+<?php
+/**
+ * Test the Ruleset::expandRulesetReference() method.
+ *
+ * @author    Juliette Reinders Folmer <[email protected]>
+ * @copyright 2024 PHPCSStandards and contributors
+ * @license   https://github.com/PHPCSStandards/PHP_CodeSniffer/blob/master/licence.txt BSD Licence
+ */
+
+namespace PHP_CodeSniffer\Tests\Core\Ruleset;
+
+use PHP_CodeSniffer\Ruleset;
+use PHP_CodeSniffer\Tests\ConfigDouble;
+use PHP_CodeSniffer\Tests\Core\Ruleset\AbstractRulesetTestCase;
+
+/**
+ * Test various aspects of the Ruleset::expandRulesetReference() method not covered by other tests.
+ *
+ * @covers \PHP_CodeSniffer\Ruleset::expandRulesetReference
+ */
+final class ExpandRulesetReferenceTest extends AbstractRulesetTestCase
+{
+
+    /**
+     * The Ruleset object.
+     *
+     * @var \PHP_CodeSniffer\Ruleset
+     */
+    private static $ruleset;
+
+
+    /**
+     * Initialize the config and ruleset objects for this test only once (but do allow recording code coverage).
+     *
+     * @xxbefore
+     *
+     * @return void
+     */
+    protected function initializeConfigAndRuleset()
+    {
+        // @phpstan-ignore isset.property, identical.alwaysFalse
+        if (isset(self::$ruleset) === false) {
+            // Set up the ruleset.
+            $standard      = __DIR__."/ExpandRulesetReferenceTest.xml";
+            $config        = new ConfigDouble(["--standard=$standard"]);
+            self::$ruleset = new Ruleset($config);
+        }
+
+    }//end initializeConfigAndRuleset()
+
+
+	public function testEverythingElse()
+	{
+        // Set up the ruleset.
+        $standard      = __DIR__."/ExpandRulesetReferenceTest.xml";
+        $config        = new ConfigDouble(["--standard=$standard"]);
+        $ruleset = new Ruleset($config);
+	}
+
+}//end class

tests/Core/Ruleset/ExpandRulesetReferenceTest.xml

@@ -0,0 +1,7 @@
+<?xml version="1.0"?>
+<ruleset xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" name="ExpandRulesetReferenceTest" xsi:noNamespaceSchemaLocation="https://raw.githubusercontent.com/PHPCSStandards/PHP_CodeSniffer/master/phpcs.xsd">
+
+    <!-- LINE 993-994 ?? test ONLINE Including a category of sniffs via a ruleset relative directory ref. -->
+    <rule ref="./fixtures/teststandard/sniffs/validsniffs"/>
+
+</ruleset>