diff --git a/tests/Core/Files/FileList/AbstractFileListTestCase.php b/tests/Core/Files/FileList/AbstractFileListTestCase.php
deleted file mode 100644
index abced07317..0000000000
--- a/tests/Core/Files/FileList/AbstractFileListTestCase.php
+++ /dev/null
@@ -1,55 +0,0 @@
-<?php
-/**
- * Abstract testcase class for testing FileList methods.
- *
- * @copyright 2025 PHPCSStandards Contributors
- * @license   https://github.com/PHPCSStandards/PHP_CodeSniffer/blob/master/licence.txt BSD Licence
- */
-
-namespace PHP_CodeSniffer\Tests\Core\Files\FileList;
-
-use PHP_CodeSniffer\Ruleset;
-use PHP_CodeSniffer\Tests\ConfigDouble;
-use PHPUnit\Framework\TestCase;
-
-/**
- * Base functionality and utilities for testing FileList methods.
- */
-abstract class AbstractFileListTestCase extends TestCase
-{
-
-    /**
-     * The Config object.
-     *
-     * @var \PHP_CodeSniffer\Config
-     */
-    protected static $config;
-
-    /**
-     * The Ruleset object.
-     *
-     * @var \PHP_CodeSniffer\Ruleset
-     */
-    protected static $ruleset;
-
-
-    /**
-     * Initialize the config and ruleset objects only once.
-     *
-     * @beforeClass
-     *
-     * @return void
-     */
-    public static function initializeConfigAndRuleset()
-    {
-        // Wrapped in an `isset()` as the properties may have been set already (via a call to this method from a dataprovider).
-        if (isset(self::$ruleset) === false) {
-            self::$config         = new ConfigDouble();
-            self::$config->filter = __DIR__.'/FilterDouble.php';
-            self::$ruleset        = new Ruleset(self::$config);
-        }
-
-    }//end initializeConfigAndRuleset()
-
-
-}//end class
diff --git a/tests/Core/Files/FileList/AddFileTest.php b/tests/Core/Files/FileList/AddFileTest.php
deleted file mode 100644
index 4346fbbf95..0000000000
--- a/tests/Core/Files/FileList/AddFileTest.php
+++ /dev/null
@@ -1,138 +0,0 @@
-<?php
-/**
- * Tests for the \PHP_CodeSniffer\Files\FileList::addFile method.
- *
- * @copyright 2025 PHPCSStandards Contributors
- * @license   https://github.com/PHPCSStandards/PHP_CodeSniffer/blob/master/licence.txt BSD Licence
- */
-
-namespace PHP_CodeSniffer\Tests\Core\Files\FileList;
-
-use PHP_CodeSniffer\Files\File;
-use PHP_CodeSniffer\Files\FileList;
-use PHP_CodeSniffer\Ruleset;
-use PHP_CodeSniffer\Tests\ConfigDouble;
-
-/**
- * Tests for the \PHP_CodeSniffer\Files\FileList::addFile method.
- *
- * @covers \PHP_CodeSniffer\Files\FileList::addFile
- */
-final class AddFileTest extends AbstractFileListTestCase
-{
-
-    /**
-     * The FileList object.
-     *
-     * @var \PHP_CodeSniffer\Files\FileList
-     */
-    private $fileList;
-
-
-    /**
-     * Initialize the FileList object.
-     *
-     * @before
-     *
-     * @return void
-     */
-    protected function initializeFileList()
-    {
-        self::$config->files = [];
-        $this->fileList      = new FileList(self::$config, self::$ruleset);
-
-    }//end initializeFileList()
-
-
-    /**
-     * Test adding a file to the list.
-     *
-     * @param string      $fileName   The name of the file to add.
-     * @param object|null $fileObject An optional file object to add instead of creating a new one.
-     *
-     * @dataProvider dataAddFile
-     *
-     * @return void
-     */
-    public function testAddFile($fileName, $fileObject=null)
-    {
-        $this->assertCount(0, $this->fileList);
-
-        $this->fileList->addFile($fileName, $fileObject);
-
-        $fileListArray = iterator_to_array($this->fileList);
-
-        $this->assertCount(1, $this->fileList, 'File count mismatch');
-        $this->assertArrayHasKey($fileName, $fileListArray, 'File not found in list');
-
-        if (isset($fileObject) === true) {
-            $this->assertSame($fileObject, $fileListArray[$fileName], 'File object mismatch');
-        } else {
-            $this->assertInstanceOf(
-                'PHP_CodeSniffer\Files\File',
-                $fileListArray[$fileName],
-                'File object not found in list'
-            );
-        }
-
-    }//end testAddFile()
-
-
-    /**
-     * Data provider for testAddFile.
-     *
-     * @return array<string, array<string, string|object>>
-     */
-    public static function dataAddFile()
-    {
-        self::initializeConfigAndRuleset();
-
-        return [
-            'Regular file'                  => [
-                'fileName' => 'test1.php',
-            ],
-            'STDIN'                         => [
-                'fileName' => 'STDIN',
-            ],
-            'Regular file with file object' => [
-                'fileName'   => 'test1.php',
-                'fileObject' => new File('test1.php', self::$ruleset, self::$config),
-            ],
-        ];
-
-    }//end dataAddFile()
-
-
-    /**
-     * Test that it is not possible to add the same file twice.
-     *
-     * @return void
-     */
-    public function testAddFileShouldNotAddTheSameFileTwice()
-    {
-        $file1         = 'test1.php';
-        $file2         = 'test2.php';
-        $expectedFiles = [
-            $file1,
-            $file2,
-        ];
-
-        // Add $file1 once.
-        $this->fileList->addFile($file1);
-        $this->assertCount(1, $this->fileList);
-        $this->assertSame([$file1], array_keys(iterator_to_array($this->fileList)));
-
-        // Try to add $file1 again. Should be ignored.
-        $this->fileList->addFile($file1);
-        $this->assertCount(1, $this->fileList);
-        $this->assertSame([$file1], array_keys(iterator_to_array($this->fileList)));
-
-        // Add $file2. Should be added.
-        $this->fileList->addFile($file2);
-        $this->assertCount(2, $this->fileList);
-        $this->assertSame($expectedFiles, array_keys(iterator_to_array($this->fileList)));
-
-    }//end testAddFileShouldNotAddTheSameFileTwice()
-
-
-}//end class
diff --git a/tests/Core/Files/FileList/ConstructTest.php b/tests/Core/Files/FileList/ConstructTest.php
deleted file mode 100644
index f40a400993..0000000000
--- a/tests/Core/Files/FileList/ConstructTest.php
+++ /dev/null
@@ -1,122 +0,0 @@
-<?php
-/**
- * Tests for the \PHP_CodeSniffer\Files\FileList::__construct method.
- *
- * @copyright 2025 PHPCSStandards Contributors
- * @license   https://github.com/PHPCSStandards/PHP_CodeSniffer/blob/master/licence.txt BSD Licence
- */
-
-namespace PHP_CodeSniffer\Tests\Core\Files\FileList;
-
-use PHP_CodeSniffer\Files\FileList;
-
-/**
- * Tests for the \PHP_CodeSniffer\Files\FileList::__construct method.
- *
- * @covers \PHP_CodeSniffer\Files\FileList::__construct
- */
-final class ConstructTest extends AbstractFileListTestCase
-{
-
-
-    /**
-     * Test the __construct() method.
-     *
-     * @param array<string> $files         List of file paths in the Config class.
-     * @param array<string> $expectedFiles List of expected file paths in the FileList.
-     *
-     * @dataProvider dataConstruct
-     *
-     * @return void
-     */
-    public function testConstruct($files, $expectedFiles)
-    {
-        self::$config->files = $files;
-
-        $fileList = new FileList(self::$config, self::$ruleset);
-
-        $this->assertSame(self::$config, $fileList->config, 'Config object mismatch');
-        $this->assertSame(self::$ruleset, $fileList->ruleset, 'Ruleset object mismatch');
-
-        $this->assertCount(count($expectedFiles), $fileList, 'File count mismatch');
-
-        $i = 0;
-
-        // Sort the values 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.
-        $fileListArray = iterator_to_array($fileList);
-        ksort($fileListArray);
-
-        foreach ($fileListArray as $filePath => $fileObject) {
-            $this->assertSame(
-                $expectedFiles[$i],
-                $filePath,
-                sprintf('File path mismatch: expected "%s", got "%s"', $expectedFiles[$i], $filePath)
-            );
-            $this->assertInstanceOf(
-                'PHP_CodeSniffer\Files\File',
-                $fileObject,
-                sprintf('File object for "%s" is not an instance of PHP_CodeSniffer\Files\File', $filePath)
-            );
-            $i++;
-        }
-
-    }//end testConstruct()
-
-
-    /**
-     * Data provider for testConstruct.
-     *
-     * @return array<string, array<string, array<string>>>
-     */
-    public static function dataConstruct()
-    {
-        $fixturesDir = __DIR__.DIRECTORY_SEPARATOR.'Fixtures'.DIRECTORY_SEPARATOR;
-
-        return [
-            'No files'                                     => [
-                'files'         => [],
-                'expectedFiles' => [],
-            ],
-            'Two files'                                    => [
-                'files'         => [
-                    'file1.php',
-                    'file2.php',
-                ],
-                'expectedFiles' => [
-                    'file1.php',
-                    'file2.php',
-                ],
-            ],
-            'A directory'                                  => [
-                'files'         => [$fixturesDir],
-                'expectedFiles' => [
-                    $fixturesDir.'file1.php',
-                    $fixturesDir.'file2.php',
-                ],
-            ],
-            'Same file twice'                              => [
-                'files'         => [
-                    'file1.php',
-                    'file1.php',
-                ],
-                'expectedFiles' => [
-                    'file1.php',
-                ],
-            ],
-            'File and then directory containing that file' => [
-                'files'         => [
-                    $fixturesDir.'file1.php',
-                    $fixturesDir,
-                ],
-                'expectedFiles' => [
-                    $fixturesDir.'file1.php',
-                    $fixturesDir.'file2.php',
-                ],
-            ],
-        ];
-
-    }//end dataConstruct()
-
-
-}//end class
diff --git a/tests/Core/Files/FileList/FilterDouble.php b/tests/Core/Files/FileList/FilterDouble.php
deleted file mode 100644
index 99952ef63c..0000000000
--- a/tests/Core/Files/FileList/FilterDouble.php
+++ /dev/null
@@ -1,31 +0,0 @@
-<?php
-/**
- * Double of the filter class that will accept every file. Used in the FileList tests.
- *
- * @copyright 2025 PHPCSStandards Contributors
- * @license   https://github.com/PHPCSStandards/PHP_CodeSniffer/blob/master/licence.txt BSD Licence
- */
-
-namespace PHP_CodeSniffer\Tests\Core\Files\FileList;
-
-use PHP_CodeSniffer\Filters\Filter;
-use ReturnTypeWillChange;
-
-final class FilterDouble extends Filter
-{
-
-
-    /**
-     * Accepts every file.
-     *
-     * @return true
-     */
-    #[ReturnTypeWillChange]
-    public function accept()
-    {
-        return true;
-
-    }//end accept()
-
-
-}//end class
diff --git a/tests/Core/Files/FileList/Fixtures/file1.php b/tests/Core/Files/FileList/Fixtures/file1.php
deleted file mode 100644
index ddec29a689..0000000000
--- a/tests/Core/Files/FileList/Fixtures/file1.php
+++ /dev/null
@@ -1,3 +0,0 @@
-<?php
-
-// Empty file for testing purposes.
diff --git a/tests/Core/Files/FileList/Fixtures/file2.php b/tests/Core/Files/FileList/Fixtures/file2.php
deleted file mode 100644
index ddec29a689..0000000000
--- a/tests/Core/Files/FileList/Fixtures/file2.php
+++ /dev/null
@@ -1,3 +0,0 @@
-<?php
-
-// Empty file for testing purposes.