Tests: Fix leakage in WP_List_Table tests.

Fixes `WP_List_table` tests leaking into other tests by:

* Restores the original `$hook_suffix` global value.
Rather than modifying the global for all tests, it now restores the original value between tests. Why? To ensure each test starts at a known state.

* Uses a new instance of `WP_List_Table` for each test.
A test may modify the `$list_table` object. If it does, it could impact tests yet to run. By instantiating a new instance in the `set_up()` test fixture, each test is isolated from the others.

Follow-up to [53868], [54215].

Props hellofromTonya, antonvlasenko.
See #58955, #58896.

git-svn-id: https://develop.svn.wordpress.org/trunk@56348 602fd350-edb4-49c9-b593-d223f7449a82

Author: hellofromtonya

tests/phpunit/tests/admin/wpListTable.php

@@ -12,17 +12,34 @@ class Tests_Admin_WpListTable extends WP_UnitTestCase {
 	 *
 	 * @var WP_List_Table $list_table
 	 */
-	protected static $list_table;
+	private $list_table;
 
-	public static function set_up_before_class() {
-		global $hook_suffix;
+	/**
+	 * Original value of $GLOBALS['hook_suffix'].
+	 *
+	 * @var string
+	 */
+	private static $original_hook_suffix;
 
+	public static function set_up_before_class() {
 		parent::set_up_before_class();
 
+		static::$original_hook_suffix = $GLOBALS['hook_suffix'];
+
 		require_once ABSPATH . 'wp-admin/includes/class-wp-list-table.php';
+	}
 
+	public function set_up() {
+		parent::set_up();
+		global $hook_suffix;
 		$hook_suffix      = '_wp_tests';
-		self::$list_table = new WP_List_Table();
+		$this->list_table = new WP_List_Table();
+	}
+
+	public function clean_up_global_scope() {
+		global $hook_suffix;
+		$hook_suffix = static::$original_hook_suffix;
+		parent::clean_up_global_scope();
 	}
 
 	/**
@@ -142,10 +159,10 @@ public function data_should_only_add_primary_column_when_needed() {
 	 * @param array $expected
 	 */
 	public function test_get_views_links( $link_data, $expected ) {
-		$get_views_links = new ReflectionMethod( self::$list_table, 'get_views_links' );
+		$get_views_links = new ReflectionMethod( $this->list_table, 'get_views_links' );
 		$get_views_links->setAccessible( true );
 
-		$actual = $get_views_links->invokeArgs( self::$list_table, array( $link_data ) );
+		$actual = $get_views_links->invokeArgs( $this->list_table, array( $link_data ) );
 
 		$this->assertSameSetsWithIndex( $expected, $actual );
 	}
@@ -257,9 +274,9 @@ public function data_get_views_links() {
 	 * }
 	 */
 	public function test_get_views_links_doing_it_wrong( $link_data ) {
-		$get_views_links = new ReflectionMethod( self::$list_table, 'get_views_links' );
+		$get_views_links = new ReflectionMethod( $this->list_table, 'get_views_links' );
 		$get_views_links->setAccessible( true );
-		$get_views_links->invokeArgs( self::$list_table, array( $link_data ) );
+		$get_views_links->invokeArgs( $this->list_table, array( $link_data ) );
 	}
 
 	/**