Add test for processing hidden files

Author: jnoordsij

tests/Core/Filters/Filter/ShouldProcessHiddenFileTest.php

@@ -0,0 +1,64 @@
+<?php
+/**
+ * Tests for the \PHP_CodeSniffer\Filters\Filter class.
+ *
+ * @copyright 2025 PHPCSStandards and contributors
+ * @license   https://github.com/PHPCSStandards/PHP_CodeSniffer/blob/HEAD/licence.txt BSD Licence
+ */
+
+namespace PHP_CodeSniffer\Tests\Core\Filters\Filter;
+
+use PHP_CodeSniffer\Filters\Filter;
+use PHP_CodeSniffer\Tests\Core\Filters\AbstractFilterTestCase;
+use RecursiveArrayIterator;
+
+/**
+ * Tests handling of hidden files.
+ *
+ * @covers \PHP_CodeSniffer\Filters\Filter
+ */
+final class ShouldProcessHiddenFileTest extends AbstractFilterTestCase
+{
+
+
+    /**
+     * Verify that if a hidden is explicitly requested for scan, it is accepted.
+     *
+     * @return void
+     */
+    public function testHiddenFileIsAcceptedWhenExplicitlyRequested()
+    {
+        $hiddenFile = self::getBaseDir() . '/.config.php';
+
+        $fakeDI = new RecursiveArrayIterator([$hiddenFile]);
+        $filter = new Filter($fakeDI, $hiddenFile, self::$config, self::$ruleset);
+
+        $this->assertSame([$hiddenFile], $this->getFilteredResultsAsArray($filter));
+    }
+
+
+    /**
+     * Verify that when (recursively) scanning a directory, hidden files are filtered out.
+     *
+     * @return void
+     */
+    public function testHiddenFileIsRejectedWhenRecursingDirectory()
+    {
+        $baseDir      = self::getBaseDir();
+        $fakeFileList = [
+            $baseDir . '/.config.php',
+            $baseDir . '/autoload.php',
+            $baseDir . '/scripts',
+            $baseDir . '/scripts/.script-config.php',
+        ];
+        $fakeDI       = new RecursiveArrayIterator($fakeFileList);
+        $filter       = new Filter($fakeDI, self::getBaseDir(), self::$config, self::$ruleset);
+
+        $expectedOutput = [
+            $baseDir . '/autoload.php',
+            $baseDir . '/scripts',
+        ];
+
+        $this->assertSame($expectedOutput, $this->getFilteredResultsAsArray($filter));
+    }
+}