diff --git a/composer.lock b/composer.lock
index fbd26f92d..b08f92ac7 100644
--- a/composer.lock
+++ b/composer.lock
@@ -1102,7 +1102,7 @@
         },
         {
             "name": "plugin-check/phpcs-sniffs",
-            "version": "dev-1009-require-users-to-write-readmetxt-in-english",
+            "version": "dev-665-check-asks-users-to-editwrite-to-plugin-use-uploads-folder",
             "dist": {
                 "type": "path",
                 "url": "./phpcs-sniffs",
diff --git a/includes/Checker/Checks/Plugin_Repo/Write_File_Check.php b/includes/Checker/Checks/Plugin_Repo/Write_File_Check.php
new file mode 100644
index 000000000..6ceb1420f
--- /dev/null
+++ b/includes/Checker/Checks/Plugin_Repo/Write_File_Check.php
@@ -0,0 +1,88 @@
+<?php
+/**
+ * Class Write_File.
+ *
+ * @package plugin-check
+ */
+
+namespace WordPress\Plugin_Check\Checker\Checks\Plugin_Repo;
+
+use WordPress\Plugin_Check\Checker\Check_Categories;
+use WordPress\Plugin_Check\Checker\Check_Result;
+use WordPress\Plugin_Check\Checker\Checks\Abstract_PHP_CodeSniffer_Check;
+use WordPress\Plugin_Check\Traits\Amend_Check_Result;
+use WordPress\Plugin_Check\Traits\Stable_Check;
+
+/**
+ * Check to detect loading files from external sites.
+ *
+ * @since n.e.x.t.
+ */
+class Write_File_Check extends Abstract_PHP_CodeSniffer_Check {
+
+	use Amend_Check_Result;
+	use Stable_Check;
+
+	/**
+	 * Bitwise flags to control check behavior.
+	 *
+	 * @since n.e.x.t.
+	 * @var int
+	 */
+	protected $flags = 0;
+
+	/**
+	 * Gets the categories for the check.
+	 *
+	 * Every check must have at least one category.
+	 *
+	 * @since n.e.x.t.
+	 *
+	 * @return array The categories for the check.
+	 */
+	public function get_categories() {
+		return array( Check_Categories::CATEGORY_PLUGIN_REPO );
+	}
+
+	/**
+	 * Returns an associative array of arguments to pass to PHPCS.
+	 *
+	 * @since 1.0.0
+	 *
+	 * @param Check_Result $result The check result to amend.
+	 * @return array An associative array of PHPCS CLI arguments.
+	 */
+	protected function get_args( Check_Result $result ) {
+		return array(
+			'extensions' => 'php',
+			'standard'   => 'PluginCheck',
+			'sniffs'     => 'PluginCheck.CodeAnalysis.WriteFile',
+		);
+	}
+
+	/**
+	 * Gets the description for the check.
+	 *
+	 * Every check must have a short description explaining what the check does.
+	 *
+	 * @since n.e.x.t.
+	 *
+	 * @return string Description.
+	 */
+	public function get_description(): string {
+		return __( 'Detects if plugins save data in the plugin folder instead of using the uploads directory or database.', 'plugin-check' );
+	}
+
+	/**
+	 * Gets the documentation URL for the check.
+	 *
+	 * Every check must have a URL with further information about the check.
+	 *
+	 * @since n.e.x.t.
+	 *
+	 * @return string The documentation URL.
+	 */
+	public function get_documentation_url(): string {
+		return __( 'https://developer.wordpress.org/plugins/wordpress-org/common-issues/#saving-data-in-the-plugin-folder', 'plugin-check' );
+	}
+}
diff --git a/includes/Checker/Default_Check_Repository.php b/includes/Checker/Default_Check_Repository.php
index daa258844..524b863c2 100644
--- a/includes/Checker/Default_Check_Repository.php
+++ b/includes/Checker/Default_Check_Repository.php
@@ -95,6 +95,7 @@ private function register_default_checks() {
 				'trademarks'                 => new Checks\Plugin_Repo\Trademarks_Check(),
 				'non_blocking_scripts'       => new Checks\Performance\Non_Blocking_Scripts_Check(),
 				'offloading_files'           => new Checks\Plugin_Repo\Offloading_Files_Check(),
+				'write_file'                 => new Checks\Plugin_Repo\Write_File_Check(),
 				'setting_sanitization'       => new Checks\Plugin_Repo\Setting_Sanitization_Check(),
 				'prefixing'                  => new Checks\Plugin_Repo\Prefixing_Check(),
 				'direct_db'                  => new Checks\Security\Direct_DB_Check(),
diff --git a/phpcs-sniffs/PluginCheck/Sniffs/CodeAnalysis/WriteFileSniff.php b/phpcs-sniffs/PluginCheck/Sniffs/CodeAnalysis/WriteFileSniff.php
new file mode 100644
index 000000000..d818372de
--- /dev/null
+++ b/phpcs-sniffs/PluginCheck/Sniffs/CodeAnalysis/WriteFileSniff.php
@@ -0,0 +1,200 @@
+<?php
+/**
+ * WriteFileSniff
+ *
+ * Based on code from {@link https://github.com/WordPress/WordPress-Coding-Standards}
+ * which is licensed under {@link https://opensource.org/licenses/MIT}.
+ *
+ * @package PluginCheck
+ */
+
+namespace PluginCheckCS\PluginCheck\Sniffs\CodeAnalysis;
+
+use PHP_CodeSniffer\Util\Tokens;
+use PHPCSUtils\Utils\PassedParameters;
+use WordPressCS\WordPress\AbstractFunctionParameterSniff;
+
+/**
+ * Verifies plugins don't save data in the plugin folder.
+ *
+ * Plugin folders are deleted when upgraded, so using them to store any data is problematic.
+ * Plugins should use the uploads directory or the database instead.
+ *
+ * @link https://developer.wordpress.org/plugins/wordpress-org/detailed-plugin-guidelines/
+ *
+ * @since 1.1.0
+ */
+final class WriteFileSniff extends AbstractFunctionParameterSniff {
+
+	/**
+	 * The group name for this group of functions.
+	 *
+	 * @since 1.1.0
+	 *
+	 * @var string
+	 */
+	protected $group_name = 'file_write';
+
+	/**
+	 * List of file write functions that need to be checked.
+	 *
+	 * @since 1.1.0
+	 *
+	 * @var array<string, true> Key is function name, value irrelevant.
+	 */
+	protected $target_functions = array(
+		// File write functions - check first parameter (file path).
+		'fwrite'            => true,
+		'fputs'             => true,
+		'file_put_contents' => true,
+		'touch'             => true,
+		// File copy/move functions - check second parameter (destination path).
+		'copy'              => true,
+		'rename'            => true,
+		'copy_dir'          => true,
+		'move_dir'          => true,
+		'unzip_file'        => true,
+	);
+
+	/**
+	 * Parameter positions for each function.
+	 *
+	 * @var array<string, int>
+	 */
+	private $param_positions = array(
+		'fwrite'            => 1,
+		'fputs'             => 1,
+		'file_put_contents' => 1,
+		'touch'             => 1,
+		'copy'              => 2,
+		'rename'            => 2,
+		'copy_dir'          => 2,
+		'move_dir'          => 2,
+		'unzip_file'        => 2,
+	);
+
+	/**
+	 * WordPress constants that indicate plugin directory usage.
+	 *
+	 * @var array
+	 */
+	private $plugin_constants = array(
+		'WP_PLUGIN_DIR',
+		'WP_PLUGIN_URL',
+		'PLUGINDIR',
+		'WPINC',
+		'WP_CONTENT_DIR',
+		'WP_CONTENT_URL',
+	);
+
+	/**
+	 * WordPress functions that indicate plugin directory usage.
+	 *
+	 * @var array
+	 */
+	private $plugin_functions = array(
+		'plugins_url',
+		'plugin_dir_path',
+		'plugin_dir_url',
+	);
+
+	/**
+	 * WordPress functions that indicate safe directory usage (uploads, temp).
+	 *
+	 * @var array
+	 */
+	private $safe_functions = array(
+		'wp_upload_dir',
+		'wp_tempnam',
+		'get_temp_dir',
+	);
+
+	/**
+	 * Process the parameters of a matched function.
+	 *
+	 * @since 1.1.0
+	 *
+	 * @param int    $stackPtr        The position of the current token in the stack.
+	 * @param string $group_name      The name of the group which was matched.
+	 * @param string $matched_content The token content (function name) which was matched in lowercase.
+	 * @param array  $parameters      Array with information about the parameters.
+	 *
+	 * @return void
+	 */
+	public function process_parameters( $stackPtr, $group_name, $matched_content, $parameters ) {
+		$param_position = isset( $this->param_positions[ $matched_content ] ) ? $this->param_positions[ $matched_content ] : 1;
+		$path_param     = PassedParameters::getParameterFromStack( $parameters, $param_position, array() );
+
+		if ( false === $path_param ) {
+			return;
+		}
+
+		// Get the content of the parameter.
+		$path_content = '';
+		for ( $i = $path_param['start']; $i <= $path_param['end']; $i++ ) {
+			if ( isset( Tokens::$emptyTokens[ $this->tokens[ $i ]['code'] ] ) ) {
+				continue;
+			}
+			$path_content .= $this->tokens[ $i ]['content'];
+		}
+
+		// Check if the path uses safe functions (uploads directory or temp).
+		foreach ( $this->safe_functions as $safe_func ) {
+			if ( stripos( $path_content, $safe_func ) !== false ) {
+				// Safe function detected, no error needed.
+				return;
+			}
+		}
+
+		// Check for plugin constants.
+		foreach ( $this->plugin_constants as $constant ) {
+			if ( stripos( $path_content, $constant ) !== false ) {
+				$this->add_error( $stackPtr, $matched_content, $path_param['start'], 'constant ' . $constant );
+				return;
+			}
+		}
+
+		// Check for plugin functions.
+		foreach ( $this->plugin_functions as $func ) {
+			if ( stripos( $path_content, $func ) !== false ) {
+				$this->add_error( $stackPtr, $matched_content, $path_param['start'], 'function ' . $func . '()' );
+				return;
+			}
+		}
+
+		// Check for __FILE__ or __DIR__ magic constants.
+		if ( stripos( $path_content, '__FILE__' ) !== false || stripos( $path_content, '__DIR__' ) !== false ) {
+			$this->add_error( $stackPtr, $matched_content, $path_param['start'], '__FILE__ or __DIR__ magic constant' );
+			return;
+		}
+
+		// Check for ABSPATH usage (could be writing to WordPress root or plugin folder).
+		if ( stripos( $path_content, 'ABSPATH' ) !== false ) {
+			$this->phpcsFile->addWarning(
+				'Writing files using ABSPATH may be problematic. Consider using wp_upload_dir() instead if storing user data or generated files.',
+				$path_param['start'],
+				'ABSPATHDetected'
+			);
+			return;
+		}
+	}
+
+	/**
+	 * Adds an error message for plugin directory write attempt.
+	 *
+	 * @param int    $stackPtr        The position of the function call.
+	 * @param string $function_name   The name of the function being called.
+	 * @param int    $error_ptr       The position to report the error.
+	 * @param string $indicator       What indicated this is a plugin path.
+	 *
+	 * @return void
+	 */
+	private function add_error( $stackPtr, $function_name, $error_ptr, $indicator ) {
+		$this->phpcsFile->addError(
+			'Plugin folders are deleted when upgraded. Do not save data to the plugin folder using %s(). Detected usage of %s. Use wp_upload_dir() to get the uploads directory path or save to the database instead.',
+			$error_ptr,
+			'PluginDirectoryWrite',
+			array( $function_name, $indicator )
+		);
+	}
+}
diff --git a/phpcs-sniffs/PluginCheck/Tests/CodeAnalysis/WriteFileUnitTest.inc b/phpcs-sniffs/PluginCheck/Tests/CodeAnalysis/WriteFileUnitTest.inc
new file mode 100644
index 000000000..1d024aa56
--- /dev/null
+++ b/phpcs-sniffs/PluginCheck/Tests/CodeAnalysis/WriteFileUnitTest.inc
@@ -0,0 +1,33 @@
+<?php
+// Test file for WriteFileSniff.
+
+// Error: Writing to plugin directory using __FILE__.
+file_put_contents( dirname( __FILE__ ) . '/cache/data.txt', 'Some data' );
+
+// Error: Writing to plugin directory using __DIR__.
+fwrite( fopen( __DIR__ . '/logs/debug.log', 'w' ), 'Debug info' );
+
+// Error: Writing using plugin_dir_path().
+fputs( fopen( plugin_dir_path( __FILE__ ) . 'error.log', 'a' ), 'Error message' );
+
+// Error: Copying to plugin directory using WP_PLUGIN_DIR.
+copy( '/tmp/file.txt', WP_PLUGIN_DIR . '/test-plugin/backup.txt' );
+
+// Error: Moving files to plugin directory.
+rename( '/tmp/temp.txt', plugin_dir_path( __FILE__ ) . 'moved.txt' );
+
+// Error: Using WP_CONTENT_DIR.
+touch( WP_CONTENT_DIR . '/custom-data.txt' );
+
+// Error: Using plugins_url (should error).
+file_put_contents( plugins_url() . '/test-plugin/data.json', '{}' );
+
+// OK: Writing to uploads directory (no error).
+file_put_contents( wp_upload_dir()['basedir'] . '/my-plugin/data.txt', 'Some data' );
+
+// OK: Using temporary directory (no error).
+fwrite( fopen( wp_tempnam( 'my-plugin-' ), 'w' ), 'Temporary data' );
+
+// OK: Using get_temp_dir (no error).
+touch( get_temp_dir() . 'my-temp-file.txt' );
+
diff --git a/phpcs-sniffs/PluginCheck/Tests/CodeAnalysis/WriteFileUnitTest.php b/phpcs-sniffs/PluginCheck/Tests/CodeAnalysis/WriteFileUnitTest.php
new file mode 100644
index 000000000..7dad7144e
--- /dev/null
+++ b/phpcs-sniffs/PluginCheck/Tests/CodeAnalysis/WriteFileUnitTest.php
@@ -0,0 +1,64 @@
+<?php
+/**
+ * Unit tests for WriteFileSniff.
+ *
+ * @package PluginCheck
+ */
+
+namespace PluginCheckCS\PluginCheck\Tests\CodeAnalysis;
+
+use PluginCheckCS\PluginCheck\Sniffs\CodeAnalysis\WriteFileSniff;
+use PluginCheckCS\PluginCheck\Tests\AbstractSniffUnitTest;
+use PHP_CodeSniffer\Sniffs\Sniff;
+
+/**
+ * Unit tests for WriteFileSniff.
+ */
+final class WriteFileUnitTest extends AbstractSniffUnitTest {
+
+	/**
+	 * Returns the lines where errors should occur.
+	 *
+	 * @return array <int line number> => <int number of errors>
+	 */
+	public function getErrorList() {
+		return array(
+			5  => 1, // file_put_contents with __FILE__.
+			8  => 1, // fwrite with __DIR__.
+			11 => 1, // fputs with plugin_dir_path().
+			14 => 1, // copy with WP_PLUGIN_DIR.
+			17 => 1, // rename with plugin_dir_path().
+			20 => 1, // touch with WP_CONTENT_DIR.
+			23 => 1, // file_put_contents with plugins_url().
+		);
+	}
+
+	/**
+	 * Returns the lines where warnings should occur.
+	 *
+	 * @return array <int line number> => <int number of warnings>
+	 */
+	public function getWarningList() {
+		return array();
+	}
+
+	/**
+	 * Returns the fully qualified class name (FQCN) of the sniff.
+	 *
+	 * @return string The fully qualified class name of the sniff.
+	 */
+	protected function get_sniff_fqcn() {
+		return WriteFileSniff::class;
+	}
+
+	/**
+	 * Sets the parameters for the sniff.
+	 *
+	 * @throws \RuntimeException If unable to set the ruleset parameters required for the test.
+	 *
+	 * @param Sniff $sniff The sniff being tested.
+	 */
+	public function set_sniff_parameters( Sniff $sniff ) {
+	}
+}
+
diff --git a/phpcs-sniffs/PluginCheck/ruleset.xml b/phpcs-sniffs/PluginCheck/ruleset.xml
index 7b6cc0ee3..acdebd754 100644
--- a/phpcs-sniffs/PluginCheck/ruleset.xml
+++ b/phpcs-sniffs/PluginCheck/ruleset.xml
@@ -10,6 +10,7 @@
 	<rule ref="PluginCheck.CodeAnalysis.Offloading" />
 	<rule ref="PluginCheck.CodeAnalysis.RequiredFunctionParameters" />
 	<rule ref="PluginCheck.CodeAnalysis.SettingSanitization" />
+	<rule ref="PluginCheck.CodeAnalysis.WriteFile" />
 	<rule ref="PluginCheck.Security.VerifyNonce" />
 	<rule ref="PluginCheck.Security.DirectDB" />
 
diff --git a/tests/phpunit/testdata/plugins/test-plugin-write-file-with-errors/file-operations.php b/tests/phpunit/testdata/plugins/test-plugin-write-file-with-errors/file-operations.php
new file mode 100644
index 000000000..1b6cf2a86
--- /dev/null
+++ b/tests/phpunit/testdata/plugins/test-plugin-write-file-with-errors/file-operations.php
@@ -0,0 +1,24 @@
+<?php
+// File with write operations to plugin directory.
+
+// Error: Writing to plugin directory using __FILE__.
+file_put_contents( dirname( __FILE__ ) . '/cache/data.txt', 'Some data' );
+
+// Error: Writing to plugin directory using __DIR__.
+fwrite( fopen( __DIR__ . '/logs/debug.log', 'w' ), 'Debug info' );
+
+// Error: Writing using plugin_dir_path().
+fputs( fopen( plugin_dir_path( __FILE__ ) . 'error.log', 'a' ), 'Error message' );
+
+// Error: Copying to plugin directory using WP_PLUGIN_DIR.
+copy( '/tmp/file.txt', WP_PLUGIN_DIR . '/test-plugin/backup.txt' );
+
+// Error: Moving files to plugin directory.
+rename( '/tmp/temp.txt', plugin_dir_path( __FILE__ ) . 'moved.txt' );
+
+// Error: Using WP_CONTENT_DIR.
+touch( WP_CONTENT_DIR . '/custom-data.txt' );
+
+// Error: Using plugins_url.
+file_put_contents( plugins_url() . '/test-plugin/data.json', '{}' );
+
diff --git a/tests/phpunit/testdata/plugins/test-plugin-write-file-with-errors/load.php b/tests/phpunit/testdata/plugins/test-plugin-write-file-with-errors/load.php
new file mode 100644
index 000000000..caeaaf174
--- /dev/null
+++ b/tests/phpunit/testdata/plugins/test-plugin-write-file-with-errors/load.php
@@ -0,0 +1,49 @@
+<?php
+/**
+ * Plugin Name: Test Plugin Write File With Errors
+ * Plugin URI: https://github.com/WordPress/plugin-check
+ * Description: Test plugin that writes files to plugin directory (not allowed).
+ * Author: WordPress Performance Team
+ * Author URI: https://make.wordpress.org/performance/
+ * License: GPLv2 or later
+ * License URI: https://www.gnu.org/licenses/old-licenses/gpl-2.0.html
+ * Text Domain: test-plugin-write-file-with-errors
+ *
+ * @package test-plugin-write-file-with-errors
+ */
+
+// Example 1: Writing to plugin directory using __FILE__.
+function test_write_with_file_constant() {
+	file_put_contents( dirname( __FILE__ ) . '/cache/data.txt', 'Some data' );
+}
+
+// Example 2: Writing to plugin directory using __DIR__.
+function test_write_with_dir_constant() {
+	fwrite( fopen( __DIR__ . '/logs/debug.log', 'w' ), 'Debug info' );
+}
+
+// Example 3: Writing using plugin_dir_path().
+function test_write_with_plugin_dir_path() {
+	fputs( fopen( plugin_dir_path( __FILE__ ) . 'error.log', 'a' ), 'Error message' );
+}
+
+// Example 4: Copying to plugin directory using WP_PLUGIN_DIR.
+function test_copy_to_plugin_dir() {
+	copy( '/tmp/file.txt', WP_PLUGIN_DIR . '/test-plugin-write-file-with-errors/backup.txt' );
+}
+
+// Example 5: Moving files to plugin directory.
+function test_move_to_plugin_dir() {
+	rename( '/tmp/temp.txt', plugin_dir_path( __FILE__ ) . 'moved.txt' );
+}
+
+// Example 6: Using WP_CONTENT_DIR.
+function test_write_to_content_dir() {
+	touch( WP_CONTENT_DIR . '/custom-data.txt' );
+}
+
+// Example 7: Using plugins_url (should error).
+function test_write_with_plugins_url() {
+	file_put_contents( plugins_url() . '/test-plugin/data.json', '{}' );
+}
+
diff --git a/tests/phpunit/testdata/plugins/test-plugin-write-file-without-errors/load.php b/tests/phpunit/testdata/plugins/test-plugin-write-file-without-errors/load.php
new file mode 100644
index 000000000..4b80d9634
--- /dev/null
+++ b/tests/phpunit/testdata/plugins/test-plugin-write-file-without-errors/load.php
@@ -0,0 +1,75 @@
+<?php
+/**
+ * Plugin Name: Test Plugin Write File Without Errors
+ * Plugin URI: https://github.com/WordPress/plugin-check
+ * Description: Test plugin that writes files correctly to uploads directory.
+ * Author: WordPress Performance Team
+ * Author URI: https://make.wordpress.org/performance/
+ * License: GPLv2 or later
+ * License URI: https://www.gnu.org/licenses/old-licenses/gpl-2.0.html
+ * Text Domain: test-plugin-write-file-without-errors
+ *
+ * @package test-plugin-write-file-without-errors
+ */
+
+// Example 1: Writing to uploads directory (correct).
+function test_write_to_uploads() {
+	$upload_dir = wp_upload_dir();
+	$file_path  = $upload_dir['basedir'] . '/my-plugin/data.txt';
+	
+	if ( ! file_exists( dirname( $file_path ) ) ) {
+		wp_mkdir_p( dirname( $file_path ) );
+	}
+	
+	file_put_contents( $file_path, 'Some data' );
+}
+
+// Example 2: Using temporary directory (correct).
+function test_write_to_temp() {
+	$temp_file = wp_tempnam( 'my-plugin-' );
+	fwrite( fopen( $temp_file, 'w' ), 'Temporary data' );
+}
+
+// Example 3: Writing to uploads with proper path handling.
+function test_write_with_upload_dir() {
+	$upload_dir = wp_upload_dir();
+	$plugin_dir = $upload_dir['basedir'] . '/test-plugin-data';
+	
+	if ( ! file_exists( $plugin_dir ) ) {
+		wp_mkdir_p( $plugin_dir );
+	}
+	
+	$log_file = $plugin_dir . '/debug.log';
+	fputs( fopen( $log_file, 'a' ), 'Log entry' );
+}
+
+// Example 4: Copying to uploads directory (correct).
+function test_copy_to_uploads() {
+	$upload_dir = wp_upload_dir();
+	$source     = '/tmp/file.txt';
+	$dest       = $upload_dir['basedir'] . '/my-plugin/backup.txt';
+	
+	copy( $source, $dest );
+}
+
+// Example 5: Moving files to uploads directory (correct).
+function test_move_to_uploads() {
+	$upload_dir = wp_upload_dir();
+	$source     = '/tmp/temp.txt';
+	$dest       = $upload_dir['basedir'] . '/my-plugin/moved.txt';
+	
+	rename( $source, $dest );
+}
+
+// Example 6: Using get_temp_dir (correct).
+function test_write_to_get_temp_dir() {
+	$temp_dir = get_temp_dir();
+	$file     = $temp_dir . 'my-temp-file.txt';
+	touch( $file );
+}
+
+// Example 7: Saving to database instead of file (correct approach).
+function test_save_to_database() {
+	update_option( 'my_plugin_data', array( 'key' => 'value' ) );
+}
+
diff --git a/tests/phpunit/tests/Checker/Checks/Write_File_Check_Tests.php b/tests/phpunit/tests/Checker/Checks/Write_File_Check_Tests.php
new file mode 100644
index 000000000..53db3093c
--- /dev/null
+++ b/tests/phpunit/tests/Checker/Checks/Write_File_Check_Tests.php
@@ -0,0 +1,69 @@
+<?php
+/**
+ * Tests for the Write_File_Check class.
+ *
+ * @package plugin-check
+ */
+
+use WordPress\Plugin_Check\Checker\Check_Context;
+use WordPress\Plugin_Check\Checker\Check_Result;
+use WordPress\Plugin_Check\Checker\Checks\Plugin_Repo\Write_File_Check;
+
+class Write_File_Check_Tests extends WP_UnitTestCase {
+
+	public function test_run_with_errors() {
+		$write_file_check = new Write_File_Check();
+		$check_context    = new Check_Context( UNIT_TESTS_PLUGIN_DIR . 'test-plugin-write-file-with-errors/load.php' );
+		$check_result     = new Check_Result( $check_context );
+
+		$write_file_check->run( $check_result );
+
+		$errors = $check_result->get_errors();
+
+		// Should have errors for plugin directory writes.
+		$this->assertNotEmpty( $errors );
+		$this->assertArrayHasKey( 'file-operations.php', $errors );
+
+		// Check for specific error codes.
+		$error_codes = array();
+		foreach ( $errors['file-operations.php'] as $line => $columns ) {
+			foreach ( $columns as $column => $messages ) {
+				foreach ( $messages as $message ) {
+					$error_codes[] = $message['code'];
+				}
+			}
+		}
+
+		// Should detect PluginDirectoryWrite errors.
+		$this->assertContains( 'PluginCheck.CodeAnalysis.WriteFile.PluginDirectoryWrite', $error_codes );
+
+		// Should have at least 6 errors (one for each bad example).
+		$this->assertGreaterThanOrEqual( 6, $check_result->get_error_count() );
+	}
+
+	public function test_run_without_errors() {
+		$write_file_check = new Write_File_Check();
+		$check_context    = new Check_Context( UNIT_TESTS_PLUGIN_DIR . 'test-plugin-write-file-without-errors/load.php' );
+		$check_result     = new Check_Result( $check_context );
+
+		$write_file_check->run( $check_result );
+
+		$errors = $check_result->get_errors();
+
+		// Should have no errors when using wp_upload_dir() or temp directories.
+		$this->assertEmpty( $errors );
+		$this->assertSame( 0, $check_result->get_error_count() );
+	}
+
+	public function test_get_description() {
+		$check = new Write_File_Check();
+		$this->assertNotEmpty( $check->get_description() );
+	}
+
+	public function test_get_documentation_url() {
+		$check = new Write_File_Check();
+		$url   = $check->get_documentation_url();
+		$this->assertNotEmpty( $url );
+		$this->assertStringContainsString( 'developer.wordpress.org', $url );
+	}
+}