Duplicate code is one of the most pungent code smells. A rule that is often used is to re-structure code once it is duplicated in three or more places.
Common duplication problems, and corresponding solutions are:
| 1 | <?php | ||
| 20 | class Test_Admin_Menu extends WP_UnitTestCase { | ||
| 21 | |||
| 22 | /** | ||
| 23 | * Menu data fixture. | ||
| 24 | * | ||
| 25 | * @var array | ||
| 26 | */ | ||
| 27 | public static $menu_data; | ||
| 28 | |||
| 29 | /** | ||
| 30 | * Submenu data fixture. | ||
| 31 | * | ||
| 32 | * @var array | ||
| 33 | */ | ||
| 34 | public static $submenu_data; | ||
| 35 | |||
| 36 | /** | ||
| 37 | * Test domain. | ||
| 38 | * | ||
| 39 | * @var string | ||
| 40 | */ | ||
| 41 | public static $domain; | ||
| 42 | |||
| 43 | /** | ||
| 44 | * Admin menu instance. | ||
| 45 | * | ||
| 46 | * @var Admin_Menu | ||
| 47 | */ | ||
| 48 | public static $admin_menu; | ||
| 49 | |||
| 50 | /** | ||
| 51 | * Mock user ID. | ||
| 52 | * | ||
| 53 | * @var int | ||
| 54 | */ | ||
| 55 | private static $user_id = 0; | ||
| 56 | |||
| 57 | /** | ||
| 58 | * Create shared fixtures. | ||
| 59 | * | ||
| 60 | * @param WP_UnitTest_Factory $factory Fixture factory. | ||
| 61 | */ | ||
| 62 | View Code Duplication | 	public static function wpSetUpBeforeClass( $factory ) { | |
| 63 | static::$domain = ( new Status() )->get_site_suffix(); | ||
| 64 | static::$user_id = $factory->user->create( array( 'role' => 'administrator' ) ); | ||
|  | |||
| 65 | static::$menu_data = get_menu_fixture(); | ||
| 66 | static::$submenu_data = get_submenu_fixture(); | ||
| 67 | } | ||
| 68 | |||
| 69 | /** | ||
| 70 | * Set up data. | ||
| 71 | */ | ||
| 72 | View Code Duplication | 	public function setUp() { | |
| 84 | |||
| 85 | /** | ||
| 86 | * Test_Admin_Menu. | ||
| 87 | * | ||
| 88 | * @covers ::reregister_menu_items | ||
| 89 | */ | ||
| 90 | 	public function test_admin_menu_output() { | ||
| 103 | |||
| 104 | /** | ||
| 105 | * Shim wpcomsh fallback site icon. | ||
| 106 | * | ||
| 107 | * @return string | ||
| 108 | */ | ||
| 109 | 	public function wpcomsh_site_icon_url() { | ||
| 112 | |||
| 113 | /** | ||
| 114 | * Custom site icon. | ||
| 115 | * | ||
| 116 | * @return string | ||
| 117 | */ | ||
| 118 | 	public function custom_site_icon_url() { | ||
| 121 | |||
| 122 | /** | ||
| 123 | * Tests add_my_home_menu | ||
| 124 | * | ||
| 125 | * @covers ::add_my_home_menu | ||
| 126 | */ | ||
| 127 | 	public function test_add_my_home_menu() { | ||
| 149 | |||
| 150 | /** | ||
| 151 | * Tests add_stats_menu | ||
| 152 | * | ||
| 153 | * @covers ::add_stats_menu | ||
| 154 | */ | ||
| 155 | 	public function test_add_stats_menu() { | ||
| 156 | global $menu; | ||
| 157 | |||
| 158 | static::$admin_menu->add_stats_menu(); | ||
| 159 | |||
| 160 | $this->assertSame( 'https://wordpress.com/stats/day/' . static::$domain, $menu['3.86682'][2] ); | ||
| 161 | } | ||
| 162 | |||
| 163 | /** | ||
| 164 | * Tests add_upgrades_menu | ||
| 165 | * | ||
| 166 | * @covers ::add_upgrades_menu | ||
| 167 | */ | ||
| 168 | View Code Duplication | 	public function test_add_upgrades_menu() { | |
| 176 | |||
| 177 | /** | ||
| 178 | * Tests add_posts_menu | ||
| 179 | * | ||
| 180 | * @covers ::add_posts_menu | ||
| 181 | */ | ||
| 182 | View Code Duplication | 	public function test_add_posts_menu() { | |
| 190 | |||
| 191 | /** | ||
| 192 | * Tests add_media_menu | ||
| 193 | * | ||
| 194 | * @covers ::add_media_menu | ||
| 195 | */ | ||
| 196 | View Code Duplication | 	public function test_add_media_menu() { | |
| 204 | |||
| 205 | /** | ||
| 206 | * Tests add_page_menu | ||
| 207 | * | ||
| 208 | * @covers ::add_page_menu | ||
| 209 | */ | ||
| 210 | View Code Duplication | 	public function test_add_page_menu() { | |
| 218 | |||
| 219 | /** | ||
| 220 | * Tests add_custom_post_type_menu | ||
| 221 | * | ||
| 222 | * @covers ::add_custom_post_type_menu | ||
| 223 | */ | ||
| 224 | 	public function test_add_custom_post_type_menu() { | ||
| 251 | |||
| 252 | /** | ||
| 253 | * Tests add_comments_menu | ||
| 254 | * | ||
| 255 | * @covers ::add_comments_menu | ||
| 256 | */ | ||
| 257 | View Code Duplication | 	public function test_add_comments_menu() { | |
| 265 | |||
| 266 | /** | ||
| 267 | * Tests add_appearance_menu | ||
| 268 | * | ||
| 269 | * @covers ::add_appearance_menu | ||
| 270 | */ | ||
| 271 | 	public function test_add_appearance_menu() { | ||
| 281 | |||
| 282 | /** | ||
| 283 | * Tests add_plugins_menu | ||
| 284 | * | ||
| 285 | * @covers ::add_plugins_menu | ||
| 286 | */ | ||
| 287 | 	public function test_add_plugins_menu() { | ||
| 303 | |||
| 304 | /** | ||
| 305 | * Tests add_users_menu | ||
| 306 | * | ||
| 307 | * @covers ::add_users_menu | ||
| 308 | */ | ||
| 309 | 	public function test_add_users_menu() { | ||
| 350 | |||
| 351 | /** | ||
| 352 | * Tests add_tools_menu | ||
| 353 | * | ||
| 354 | * @covers ::add_tools_menu | ||
| 355 | */ | ||
| 356 | 	public function test_add_tools_menu() { | ||
| 366 | |||
| 367 | /** | ||
| 368 | * Tests add_options_menu | ||
| 369 | * | ||
| 370 | * @covers ::add_options_menu | ||
| 371 | */ | ||
| 372 | View Code Duplication | 	public function test_add_options_menu() { | |
| 379 | |||
| 380 | /** | ||
| 381 | * Tests add_jetpack_menu | ||
| 382 | * | ||
| 383 | * @covers ::add_jetpack_menu | ||
| 384 | */ | ||
| 385 | 	public function test_add_jetpack_menu() { | ||
| 394 | |||
| 395 | /** | ||
| 396 | * Tests add_gutenberg_menus | ||
| 397 | * | ||
| 398 | * @covers ::add_gutenberg_menus | ||
| 399 | */ | ||
| 400 | 	public function test_add_gutenberg_menus() { | ||
| 420 | } | ||
| 421 | 
Let’s assume you have a class which uses late-static binding:
The code above will run fine in your PHP runtime. However, if you now create a sub-class and call the
getSomeVariable()on that sub-class, you will receive a runtime error:In the case above, it makes sense to update
SomeClassto useselfinstead: