diff --git a/tests/phpunit/tests/functions/wpListSort.php b/tests/phpunit/tests/functions/wpListSort.php
new file mode 100644
index 0000000000..7159af4937
--- /dev/null
+++ b/tests/phpunit/tests/functions/wpListSort.php
@@ -0,0 +1,660 @@
+<?php
+
+/**
+ * Test wp_list_sort().
+ *
+ * @group functions.php
+ * @covers ::wp_list_sort
+ */
+class Tests_Functions_wpListSort extends WP_UnitTestCase {
+
+	/**
+	 * @dataProvider data_test_wp_list_sort
+	 *
+	 * @param string|array $orderby Either the field name to order by or an array
+	 *                              of multiple orderby fields as $orderby => $order.
+	 * @param string       $order   Either 'ASC' or 'DESC'.
+	 */
+	public function test_wp_list_sort( $list, $orderby, $order, $expected ) {
+		$this->assertSame( $expected, wp_list_sort( $list, $orderby, $order ) );
+	}
+
+	public function data_test_wp_list_sort() {
+		return array(
+			'single orderby ascending'        => array(
+				array(
+					array(
+						'foo' => 'bar',
+						'bar' => 'baz',
+						'key' => 'foo',
+					),
+					array(
+						'foo'   => 'foo',
+						'lorem' => 'ipsum',
+						'key'   => 'bar',
+					),
+					array(
+						'foo' => 'baz',
+						'key' => 'value',
+					),
+				),
+				'foo',
+				'ASC',
+				array(
+					array(
+						'foo' => 'bar',
+						'bar' => 'baz',
+						'key' => 'foo',
+					),
+					array(
+						'foo' => 'baz',
+						'key' => 'value',
+					),
+					array(
+						'foo'   => 'foo',
+						'lorem' => 'ipsum',
+						'key'   => 'bar',
+					),
+				),
+			),
+			'single orderby descending'       => array(
+				array(
+					array(
+						'foo' => 'bar',
+						'bar' => 'baz',
+						'key' => 'foo',
+					),
+					array(
+						'foo'   => 'foo',
+						'lorem' => 'ipsum',
+						'key'   => 'bar',
+					),
+					array(
+						'foo' => 'baz',
+						'key' => 'value',
+					),
+				),
+				'foo',
+				'DESC',
+				array(
+					array(
+						'foo'   => 'foo',
+						'lorem' => 'ipsum',
+						'key'   => 'bar',
+					),
+					array(
+						'foo' => 'baz',
+						'key' => 'value',
+					),
+					array(
+						'foo' => 'bar',
+						'bar' => 'baz',
+						'key' => 'foo',
+					),
+				),
+			),
+			'single orderby array ascending'  => array(
+				array(
+					array(
+						'foo' => 'bar',
+						'bar' => 'baz',
+						'key' => 'foo',
+					),
+					array(
+						'foo'   => 'foo',
+						'lorem' => 'ipsum',
+						'key'   => 'bar',
+					),
+					array(
+						'foo' => 'baz',
+						'key' => 'value',
+					),
+				),
+				array( 'foo' => 'ASC' ),
+				'IGNORED',
+				array(
+					array(
+						'foo' => 'bar',
+						'bar' => 'baz',
+						'key' => 'foo',
+					),
+					array(
+						'foo' => 'baz',
+						'key' => 'value',
+					),
+					array(
+						'foo'   => 'foo',
+						'lorem' => 'ipsum',
+						'key'   => 'bar',
+					),
+				),
+			),
+			'single orderby array descending' => array(
+				array(
+					array(
+						'foo' => 'bar',
+						'bar' => 'baz',
+						'key' => 'foo',
+					),
+					array(
+						'foo'   => 'foo',
+						'lorem' => 'ipsum',
+						'key'   => 'bar',
+					),
+					array(
+						'foo' => 'baz',
+						'key' => 'value',
+					),
+				),
+				array( 'foo' => 'DESC' ),
+				'IGNORED',
+				array(
+					array(
+						'foo'   => 'foo',
+						'lorem' => 'ipsum',
+						'key'   => 'bar',
+					),
+					array(
+						'foo' => 'baz',
+						'key' => 'value',
+					),
+					array(
+						'foo' => 'bar',
+						'bar' => 'baz',
+						'key' => 'foo',
+					),
+				),
+			),
+			'multiple orderby ascending'      => array(
+				array(
+					array(
+						'foo' => 'bar',
+						'bar' => 'baz',
+						'key' => 'foo',
+					),
+					array(
+						'foo'   => 'foo',
+						'lorem' => 'ipsum',
+						'key'   => 'bar',
+					),
+					array(
+						'foo' => 'foo',
+						'key' => 'key',
+					),
+					array(
+						'foo' => 'baz',
+						'key' => 'key',
+					),
+					array(
+						'foo' => 'bar',
+						'key' => 'value',
+					),
+				),
+				array(
+					'key' => 'ASC',
+					'foo' => 'ASC',
+				),
+				'IGNORED',
+				array(
+					array(
+						'foo'   => 'foo',
+						'lorem' => 'ipsum',
+						'key'   => 'bar',
+					),
+					array(
+						'foo' => 'bar',
+						'bar' => 'baz',
+						'key' => 'foo',
+					),
+					array(
+						'foo' => 'baz',
+						'key' => 'key',
+					),
+					array(
+						'foo' => 'foo',
+						'key' => 'key',
+					),
+					array(
+						'foo' => 'bar',
+						'key' => 'value',
+					),
+				),
+			),
+			'multiple orderby descending'     => array(
+				array(
+					array(
+						'foo' => 'bar',
+						'bar' => 'baz',
+						'key' => 'foo',
+					),
+					array(
+						'foo'   => 'foo',
+						'lorem' => 'ipsum',
+						'key'   => 'bar',
+					),
+					array(
+						'foo' => 'foo',
+						'key' => 'key',
+					),
+					array(
+						'foo' => 'baz',
+						'key' => 'key',
+					),
+					array(
+						'foo' => 'bar',
+						'key' => 'value',
+					),
+				),
+				array(
+					'key' => 'DESC',
+					'foo' => 'DESC',
+				),
+				'IGNORED',
+				array(
+					array(
+						'foo' => 'bar',
+						'key' => 'value',
+					),
+					array(
+						'foo' => 'foo',
+						'key' => 'key',
+					),
+					array(
+						'foo' => 'baz',
+						'key' => 'key',
+					),
+					array(
+						'foo' => 'bar',
+						'bar' => 'baz',
+						'key' => 'foo',
+					),
+					array(
+						'foo'   => 'foo',
+						'lorem' => 'ipsum',
+						'key'   => 'bar',
+					),
+				),
+			),
+			'multiple orderby mixed'          => array(
+				array(
+					array(
+						'foo' => 'bar',
+						'bar' => 'baz',
+						'key' => 'foo',
+					),
+					array(
+						'foo'   => 'foo',
+						'lorem' => 'ipsum',
+						'key'   => 'bar',
+					),
+					array(
+						'foo' => 'foo',
+						'key' => 'key',
+					),
+					array(
+						'foo' => 'baz',
+						'key' => 'key',
+					),
+					array(
+						'foo' => 'bar',
+						'key' => 'value',
+					),
+				),
+				array(
+					'key' => 'DESC',
+					'foo' => 'ASC',
+				),
+				'IGNORED',
+				array(
+					array(
+						'foo' => 'bar',
+						'key' => 'value',
+					),
+					array(
+						'foo' => 'baz',
+						'key' => 'key',
+					),
+					array(
+						'foo' => 'foo',
+						'key' => 'key',
+					),
+					array(
+						'foo' => 'bar',
+						'bar' => 'baz',
+						'key' => 'foo',
+					),
+					array(
+						'foo'   => 'foo',
+						'lorem' => 'ipsum',
+						'key'   => 'bar',
+					),
+				),
+			),
+		);
+	}
+
+	/**
+	 * @dataProvider data_test_wp_list_sort_preserve_keys
+	 *
+	 * @param string|array $orderby Either the field name to order by or an array
+	 *                              of multiple orderby fields as $orderby => $order.
+	 * @param string       $order   Either 'ASC' or 'DESC'.
+	 */
+	public function test_wp_list_sort_preserve_keys( $list, $orderby, $order, $expected ) {
+		$this->assertSame( $expected, wp_list_sort( $list, $orderby, $order, true ) );
+	}
+
+	public function data_test_wp_list_sort_preserve_keys() {
+		return array(
+			'single orderby ascending'        => array(
+				array(
+					'foobar' => array(
+						'foo' => 'bar',
+						'bar' => 'baz',
+						'key' => 'foo',
+					),
+					'foofoo' => array(
+						'foo'   => 'foo',
+						'lorem' => 'ipsum',
+						'key'   => 'bar',
+					),
+					'foobaz' => array(
+						'foo' => 'baz',
+						'key' => 'value',
+					),
+				),
+				'foo',
+				'ASC',
+				array(
+					'foobar' => array(
+						'foo' => 'bar',
+						'bar' => 'baz',
+						'key' => 'foo',
+					),
+					'foobaz' => array(
+						'foo' => 'baz',
+						'key' => 'value',
+					),
+					'foofoo' => array(
+						'foo'   => 'foo',
+						'lorem' => 'ipsum',
+						'key'   => 'bar',
+					),
+				),
+			),
+			'single orderby descending'       => array(
+				array(
+					'foobar' => array(
+						'foo' => 'bar',
+						'bar' => 'baz',
+						'key' => 'foo',
+					),
+					'foofoo' => array(
+						'foo'   => 'foo',
+						'lorem' => 'ipsum',
+						'key'   => 'bar',
+					),
+					'foobaz' => array(
+						'foo' => 'baz',
+						'key' => 'value',
+					),
+				),
+				'foo',
+				'DESC',
+				array(
+					'foofoo' => array(
+						'foo'   => 'foo',
+						'lorem' => 'ipsum',
+						'key'   => 'bar',
+					),
+					'foobaz' => array(
+						'foo' => 'baz',
+						'key' => 'value',
+					),
+					'foobar' => array(
+						'foo' => 'bar',
+						'bar' => 'baz',
+						'key' => 'foo',
+					),
+				),
+			),
+			'single orderby array ascending'  => array(
+				array(
+					'foobar' => array(
+						'foo' => 'bar',
+						'bar' => 'baz',
+						'key' => 'foo',
+					),
+					'foofoo' => array(
+						'foo'   => 'foo',
+						'lorem' => 'ipsum',
+						'key'   => 'bar',
+					),
+					'foobaz' => array(
+						'foo' => 'baz',
+						'key' => 'value',
+					),
+				),
+				array( 'foo' => 'ASC' ),
+				'IGNORED',
+				array(
+					'foobar' => array(
+						'foo' => 'bar',
+						'bar' => 'baz',
+						'key' => 'foo',
+					),
+					'foobaz' => array(
+						'foo' => 'baz',
+						'key' => 'value',
+					),
+					'foofoo' => array(
+						'foo'   => 'foo',
+						'lorem' => 'ipsum',
+						'key'   => 'bar',
+					),
+				),
+			),
+			'single orderby array descending' => array(
+				array(
+					'foobar' => array(
+						'foo' => 'bar',
+						'bar' => 'baz',
+						'key' => 'foo',
+					),
+					'foofoo' => array(
+						'foo'   => 'foo',
+						'lorem' => 'ipsum',
+						'key'   => 'bar',
+					),
+					'foobaz' => array(
+						'foo' => 'baz',
+						'key' => 'value',
+					),
+				),
+				array( 'foo' => 'DESC' ),
+				'IGNORED',
+				array(
+					'foofoo' => array(
+						'foo'   => 'foo',
+						'lorem' => 'ipsum',
+						'key'   => 'bar',
+					),
+					'foobaz' => array(
+						'foo' => 'baz',
+						'key' => 'value',
+					),
+					'foobar' => array(
+						'foo' => 'bar',
+						'bar' => 'baz',
+						'key' => 'foo',
+					),
+				),
+			),
+			'multiple orderby ascending'      => array(
+				array(
+					'foobarfoo'   => array(
+						'foo' => 'bar',
+						'bar' => 'baz',
+						'key' => 'foo',
+					),
+					'foofoobar'   => array(
+						'foo'   => 'foo',
+						'lorem' => 'ipsum',
+						'key'   => 'bar',
+					),
+					'foofookey'   => array(
+						'foo' => 'foo',
+						'key' => 'key',
+					),
+					'foobazkey'   => array(
+						'foo' => 'baz',
+						'key' => 'key',
+					),
+					'foobarvalue' => array(
+						'foo' => 'bar',
+						'key' => 'value',
+					),
+				),
+				array(
+					'key' => 'ASC',
+					'foo' => 'ASC',
+				),
+				'IGNORED',
+				array(
+					'foofoobar'   => array(
+						'foo'   => 'foo',
+						'lorem' => 'ipsum',
+						'key'   => 'bar',
+					),
+					'foobarfoo'   => array(
+						'foo' => 'bar',
+						'bar' => 'baz',
+						'key' => 'foo',
+					),
+					'foobazkey'   => array(
+						'foo' => 'baz',
+						'key' => 'key',
+					),
+					'foofookey'   => array(
+						'foo' => 'foo',
+						'key' => 'key',
+					),
+					'foobarvalue' => array(
+						'foo' => 'bar',
+						'key' => 'value',
+					),
+				),
+			),
+			'multiple orderby descending'     => array(
+				array(
+					'foobarfoo'   => array(
+						'foo' => 'bar',
+						'bar' => 'baz',
+						'key' => 'foo',
+					),
+					'foofoobar'   => array(
+						'foo'   => 'foo',
+						'lorem' => 'ipsum',
+						'key'   => 'bar',
+					),
+					'foofookey'   => array(
+						'foo' => 'foo',
+						'key' => 'key',
+					),
+					'foobazkey'   => array(
+						'foo' => 'baz',
+						'key' => 'key',
+					),
+					'foobarvalue' => array(
+						'foo' => 'bar',
+						'key' => 'value',
+					),
+				),
+				array(
+					'key' => 'DESC',
+					'foo' => 'DESC',
+				),
+				'IGNORED',
+				array(
+					'foobarvalue' => array(
+						'foo' => 'bar',
+						'key' => 'value',
+					),
+					'foofookey'   => array(
+						'foo' => 'foo',
+						'key' => 'key',
+					),
+					'foobazkey'   => array(
+						'foo' => 'baz',
+						'key' => 'key',
+					),
+					'foobarfoo'   => array(
+						'foo' => 'bar',
+						'bar' => 'baz',
+						'key' => 'foo',
+					),
+					'foofoobar'   => array(
+						'foo'   => 'foo',
+						'lorem' => 'ipsum',
+						'key'   => 'bar',
+					),
+				),
+			),
+			'multiple orderby mixed'          => array(
+				array(
+					'foobarfoo'   => array(
+						'foo' => 'bar',
+						'bar' => 'baz',
+						'key' => 'foo',
+					),
+					'foofoobar'   => array(
+						'foo'   => 'foo',
+						'lorem' => 'ipsum',
+						'key'   => 'bar',
+					),
+					'foofookey'   => array(
+						'foo' => 'foo',
+						'key' => 'key',
+					),
+					'foobazkey'   => array(
+						'foo' => 'baz',
+						'key' => 'key',
+					),
+					'foobarvalue' => array(
+						'foo' => 'bar',
+						'key' => 'value',
+					),
+				),
+				array(
+					'key' => 'DESC',
+					'foo' => 'ASC',
+				),
+				'IGNORED',
+				array(
+					'foobarvalue' => array(
+						'foo' => 'bar',
+						'key' => 'value',
+					),
+					'foobazkey'   => array(
+						'foo' => 'baz',
+						'key' => 'key',
+					),
+					'foofookey'   => array(
+						'foo' => 'foo',
+						'key' => 'key',
+					),
+					'foobarfoo'   => array(
+						'foo' => 'bar',
+						'bar' => 'baz',
+						'key' => 'foo',
+					),
+					'foofoobar'   => array(
+						'foo'   => 'foo',
+						'lorem' => 'ipsum',
+						'key'   => 'bar',
+					),
+				),
+			),
+		);
+	}
+}
diff --git a/tests/phpunit/tests/functions/wpListUtil.php b/tests/phpunit/tests/functions/wpListUtil.php
index 186643e72c..45cad6627a 100644
--- a/tests/phpunit/tests/functions/wpListUtil.php
+++ b/tests/phpunit/tests/functions/wpListUtil.php
@@ -1,664 +1,12 @@
 <?php
 
 /**
+ * Test WP_List_Util class.
+ *
  * @group functions.php
  */
 class Tests_Functions_wpListUtil extends WP_UnitTestCase {
 
-	public function data_test_wp_list_sort() {
-		return array(
-			'single orderby ascending'        => array(
-				array(
-					array(
-						'foo' => 'bar',
-						'bar' => 'baz',
-						'key' => 'foo',
-					),
-					array(
-						'foo'   => 'foo',
-						'lorem' => 'ipsum',
-						'key'   => 'bar',
-					),
-					array(
-						'foo' => 'baz',
-						'key' => 'value',
-					),
-				),
-				'foo',
-				'ASC',
-				array(
-					array(
-						'foo' => 'bar',
-						'bar' => 'baz',
-						'key' => 'foo',
-					),
-					array(
-						'foo' => 'baz',
-						'key' => 'value',
-					),
-					array(
-						'foo'   => 'foo',
-						'lorem' => 'ipsum',
-						'key'   => 'bar',
-					),
-				),
-			),
-			'single orderby descending'       => array(
-				array(
-					array(
-						'foo' => 'bar',
-						'bar' => 'baz',
-						'key' => 'foo',
-					),
-					array(
-						'foo'   => 'foo',
-						'lorem' => 'ipsum',
-						'key'   => 'bar',
-					),
-					array(
-						'foo' => 'baz',
-						'key' => 'value',
-					),
-				),
-				'foo',
-				'DESC',
-				array(
-					array(
-						'foo'   => 'foo',
-						'lorem' => 'ipsum',
-						'key'   => 'bar',
-					),
-					array(
-						'foo' => 'baz',
-						'key' => 'value',
-					),
-					array(
-						'foo' => 'bar',
-						'bar' => 'baz',
-						'key' => 'foo',
-					),
-				),
-			),
-			'single orderby array ascending'  => array(
-				array(
-					array(
-						'foo' => 'bar',
-						'bar' => 'baz',
-						'key' => 'foo',
-					),
-					array(
-						'foo'   => 'foo',
-						'lorem' => 'ipsum',
-						'key'   => 'bar',
-					),
-					array(
-						'foo' => 'baz',
-						'key' => 'value',
-					),
-				),
-				array( 'foo' => 'ASC' ),
-				'IGNORED',
-				array(
-					array(
-						'foo' => 'bar',
-						'bar' => 'baz',
-						'key' => 'foo',
-					),
-					array(
-						'foo' => 'baz',
-						'key' => 'value',
-					),
-					array(
-						'foo'   => 'foo',
-						'lorem' => 'ipsum',
-						'key'   => 'bar',
-					),
-				),
-			),
-			'single orderby array descending' => array(
-				array(
-					array(
-						'foo' => 'bar',
-						'bar' => 'baz',
-						'key' => 'foo',
-					),
-					array(
-						'foo'   => 'foo',
-						'lorem' => 'ipsum',
-						'key'   => 'bar',
-					),
-					array(
-						'foo' => 'baz',
-						'key' => 'value',
-					),
-				),
-				array( 'foo' => 'DESC' ),
-				'IGNORED',
-				array(
-					array(
-						'foo'   => 'foo',
-						'lorem' => 'ipsum',
-						'key'   => 'bar',
-					),
-					array(
-						'foo' => 'baz',
-						'key' => 'value',
-					),
-					array(
-						'foo' => 'bar',
-						'bar' => 'baz',
-						'key' => 'foo',
-					),
-				),
-			),
-			'multiple orderby ascending'      => array(
-				array(
-					array(
-						'foo' => 'bar',
-						'bar' => 'baz',
-						'key' => 'foo',
-					),
-					array(
-						'foo'   => 'foo',
-						'lorem' => 'ipsum',
-						'key'   => 'bar',
-					),
-					array(
-						'foo' => 'foo',
-						'key' => 'key',
-					),
-					array(
-						'foo' => 'baz',
-						'key' => 'key',
-					),
-					array(
-						'foo' => 'bar',
-						'key' => 'value',
-					),
-				),
-				array(
-					'key' => 'ASC',
-					'foo' => 'ASC',
-				),
-				'IGNORED',
-				array(
-					array(
-						'foo'   => 'foo',
-						'lorem' => 'ipsum',
-						'key'   => 'bar',
-					),
-					array(
-						'foo' => 'bar',
-						'bar' => 'baz',
-						'key' => 'foo',
-					),
-					array(
-						'foo' => 'baz',
-						'key' => 'key',
-					),
-					array(
-						'foo' => 'foo',
-						'key' => 'key',
-					),
-					array(
-						'foo' => 'bar',
-						'key' => 'value',
-					),
-				),
-			),
-			'multiple orderby descending'     => array(
-				array(
-					array(
-						'foo' => 'bar',
-						'bar' => 'baz',
-						'key' => 'foo',
-					),
-					array(
-						'foo'   => 'foo',
-						'lorem' => 'ipsum',
-						'key'   => 'bar',
-					),
-					array(
-						'foo' => 'foo',
-						'key' => 'key',
-					),
-					array(
-						'foo' => 'baz',
-						'key' => 'key',
-					),
-					array(
-						'foo' => 'bar',
-						'key' => 'value',
-					),
-				),
-				array(
-					'key' => 'DESC',
-					'foo' => 'DESC',
-				),
-				'IGNORED',
-				array(
-					array(
-						'foo' => 'bar',
-						'key' => 'value',
-					),
-					array(
-						'foo' => 'foo',
-						'key' => 'key',
-					),
-					array(
-						'foo' => 'baz',
-						'key' => 'key',
-					),
-					array(
-						'foo' => 'bar',
-						'bar' => 'baz',
-						'key' => 'foo',
-					),
-					array(
-						'foo'   => 'foo',
-						'lorem' => 'ipsum',
-						'key'   => 'bar',
-					),
-				),
-			),
-			'multiple orderby mixed'          => array(
-				array(
-					array(
-						'foo' => 'bar',
-						'bar' => 'baz',
-						'key' => 'foo',
-					),
-					array(
-						'foo'   => 'foo',
-						'lorem' => 'ipsum',
-						'key'   => 'bar',
-					),
-					array(
-						'foo' => 'foo',
-						'key' => 'key',
-					),
-					array(
-						'foo' => 'baz',
-						'key' => 'key',
-					),
-					array(
-						'foo' => 'bar',
-						'key' => 'value',
-					),
-				),
-				array(
-					'key' => 'DESC',
-					'foo' => 'ASC',
-				),
-				'IGNORED',
-				array(
-					array(
-						'foo' => 'bar',
-						'key' => 'value',
-					),
-					array(
-						'foo' => 'baz',
-						'key' => 'key',
-					),
-					array(
-						'foo' => 'foo',
-						'key' => 'key',
-					),
-					array(
-						'foo' => 'bar',
-						'bar' => 'baz',
-						'key' => 'foo',
-					),
-					array(
-						'foo'   => 'foo',
-						'lorem' => 'ipsum',
-						'key'   => 'bar',
-					),
-				),
-			),
-		);
-	}
-
-	/**
-	 * @dataProvider data_test_wp_list_sort
-	 *
-	 * @covers ::wp_list_sort
-	 *
-	 * @param string|array $orderby Either the field name to order by or an array
-	 *                              of multiple orderby fields as $orderby => $order.
-	 * @param string       $order   Either 'ASC' or 'DESC'.
-	 */
-	public function test_wp_list_sort( $list, $orderby, $order, $expected ) {
-		$this->assertSame( $expected, wp_list_sort( $list, $orderby, $order ) );
-	}
-
-	public function data_test_wp_list_sort_preserve_keys() {
-		return array(
-			'single orderby ascending'        => array(
-				array(
-					'foobar' => array(
-						'foo' => 'bar',
-						'bar' => 'baz',
-						'key' => 'foo',
-					),
-					'foofoo' => array(
-						'foo'   => 'foo',
-						'lorem' => 'ipsum',
-						'key'   => 'bar',
-					),
-					'foobaz' => array(
-						'foo' => 'baz',
-						'key' => 'value',
-					),
-				),
-				'foo',
-				'ASC',
-				array(
-					'foobar' => array(
-						'foo' => 'bar',
-						'bar' => 'baz',
-						'key' => 'foo',
-					),
-					'foobaz' => array(
-						'foo' => 'baz',
-						'key' => 'value',
-					),
-					'foofoo' => array(
-						'foo'   => 'foo',
-						'lorem' => 'ipsum',
-						'key'   => 'bar',
-					),
-				),
-			),
-			'single orderby descending'       => array(
-				array(
-					'foobar' => array(
-						'foo' => 'bar',
-						'bar' => 'baz',
-						'key' => 'foo',
-					),
-					'foofoo' => array(
-						'foo'   => 'foo',
-						'lorem' => 'ipsum',
-						'key'   => 'bar',
-					),
-					'foobaz' => array(
-						'foo' => 'baz',
-						'key' => 'value',
-					),
-				),
-				'foo',
-				'DESC',
-				array(
-					'foofoo' => array(
-						'foo'   => 'foo',
-						'lorem' => 'ipsum',
-						'key'   => 'bar',
-					),
-					'foobaz' => array(
-						'foo' => 'baz',
-						'key' => 'value',
-					),
-					'foobar' => array(
-						'foo' => 'bar',
-						'bar' => 'baz',
-						'key' => 'foo',
-					),
-				),
-			),
-			'single orderby array ascending'  => array(
-				array(
-					'foobar' => array(
-						'foo' => 'bar',
-						'bar' => 'baz',
-						'key' => 'foo',
-					),
-					'foofoo' => array(
-						'foo'   => 'foo',
-						'lorem' => 'ipsum',
-						'key'   => 'bar',
-					),
-					'foobaz' => array(
-						'foo' => 'baz',
-						'key' => 'value',
-					),
-				),
-				array( 'foo' => 'ASC' ),
-				'IGNORED',
-				array(
-					'foobar' => array(
-						'foo' => 'bar',
-						'bar' => 'baz',
-						'key' => 'foo',
-					),
-					'foobaz' => array(
-						'foo' => 'baz',
-						'key' => 'value',
-					),
-					'foofoo' => array(
-						'foo'   => 'foo',
-						'lorem' => 'ipsum',
-						'key'   => 'bar',
-					),
-				),
-			),
-			'single orderby array descending' => array(
-				array(
-					'foobar' => array(
-						'foo' => 'bar',
-						'bar' => 'baz',
-						'key' => 'foo',
-					),
-					'foofoo' => array(
-						'foo'   => 'foo',
-						'lorem' => 'ipsum',
-						'key'   => 'bar',
-					),
-					'foobaz' => array(
-						'foo' => 'baz',
-						'key' => 'value',
-					),
-				),
-				array( 'foo' => 'DESC' ),
-				'IGNORED',
-				array(
-					'foofoo' => array(
-						'foo'   => 'foo',
-						'lorem' => 'ipsum',
-						'key'   => 'bar',
-					),
-					'foobaz' => array(
-						'foo' => 'baz',
-						'key' => 'value',
-					),
-					'foobar' => array(
-						'foo' => 'bar',
-						'bar' => 'baz',
-						'key' => 'foo',
-					),
-				),
-			),
-			'multiple orderby ascending'      => array(
-				array(
-					'foobarfoo'   => array(
-						'foo' => 'bar',
-						'bar' => 'baz',
-						'key' => 'foo',
-					),
-					'foofoobar'   => array(
-						'foo'   => 'foo',
-						'lorem' => 'ipsum',
-						'key'   => 'bar',
-					),
-					'foofookey'   => array(
-						'foo' => 'foo',
-						'key' => 'key',
-					),
-					'foobazkey'   => array(
-						'foo' => 'baz',
-						'key' => 'key',
-					),
-					'foobarvalue' => array(
-						'foo' => 'bar',
-						'key' => 'value',
-					),
-				),
-				array(
-					'key' => 'ASC',
-					'foo' => 'ASC',
-				),
-				'IGNORED',
-				array(
-					'foofoobar'   => array(
-						'foo'   => 'foo',
-						'lorem' => 'ipsum',
-						'key'   => 'bar',
-					),
-					'foobarfoo'   => array(
-						'foo' => 'bar',
-						'bar' => 'baz',
-						'key' => 'foo',
-					),
-					'foobazkey'   => array(
-						'foo' => 'baz',
-						'key' => 'key',
-					),
-					'foofookey'   => array(
-						'foo' => 'foo',
-						'key' => 'key',
-					),
-					'foobarvalue' => array(
-						'foo' => 'bar',
-						'key' => 'value',
-					),
-				),
-			),
-			'multiple orderby descending'     => array(
-				array(
-					'foobarfoo'   => array(
-						'foo' => 'bar',
-						'bar' => 'baz',
-						'key' => 'foo',
-					),
-					'foofoobar'   => array(
-						'foo'   => 'foo',
-						'lorem' => 'ipsum',
-						'key'   => 'bar',
-					),
-					'foofookey'   => array(
-						'foo' => 'foo',
-						'key' => 'key',
-					),
-					'foobazkey'   => array(
-						'foo' => 'baz',
-						'key' => 'key',
-					),
-					'foobarvalue' => array(
-						'foo' => 'bar',
-						'key' => 'value',
-					),
-				),
-				array(
-					'key' => 'DESC',
-					'foo' => 'DESC',
-				),
-				'IGNORED',
-				array(
-					'foobarvalue' => array(
-						'foo' => 'bar',
-						'key' => 'value',
-					),
-					'foofookey'   => array(
-						'foo' => 'foo',
-						'key' => 'key',
-					),
-					'foobazkey'   => array(
-						'foo' => 'baz',
-						'key' => 'key',
-					),
-					'foobarfoo'   => array(
-						'foo' => 'bar',
-						'bar' => 'baz',
-						'key' => 'foo',
-					),
-					'foofoobar'   => array(
-						'foo'   => 'foo',
-						'lorem' => 'ipsum',
-						'key'   => 'bar',
-					),
-				),
-			),
-			'multiple orderby mixed'          => array(
-				array(
-					'foobarfoo'   => array(
-						'foo' => 'bar',
-						'bar' => 'baz',
-						'key' => 'foo',
-					),
-					'foofoobar'   => array(
-						'foo'   => 'foo',
-						'lorem' => 'ipsum',
-						'key'   => 'bar',
-					),
-					'foofookey'   => array(
-						'foo' => 'foo',
-						'key' => 'key',
-					),
-					'foobazkey'   => array(
-						'foo' => 'baz',
-						'key' => 'key',
-					),
-					'foobarvalue' => array(
-						'foo' => 'bar',
-						'key' => 'value',
-					),
-				),
-				array(
-					'key' => 'DESC',
-					'foo' => 'ASC',
-				),
-				'IGNORED',
-				array(
-					'foobarvalue' => array(
-						'foo' => 'bar',
-						'key' => 'value',
-					),
-					'foobazkey'   => array(
-						'foo' => 'baz',
-						'key' => 'key',
-					),
-					'foofookey'   => array(
-						'foo' => 'foo',
-						'key' => 'key',
-					),
-					'foobarfoo'   => array(
-						'foo' => 'bar',
-						'bar' => 'baz',
-						'key' => 'foo',
-					),
-					'foofoobar'   => array(
-						'foo'   => 'foo',
-						'lorem' => 'ipsum',
-						'key'   => 'bar',
-					),
-				),
-			),
-		);
-	}
-
-	/**
-	 * @dataProvider data_test_wp_list_sort_preserve_keys
-	 *
-	 * @covers ::wp_list_sort
-	 *
-	 * @param string|array $orderby Either the field name to order by or an array
-	 *                              of multiple orderby fields as $orderby => $order.
-	 * @param string       $order   Either 'ASC' or 'DESC'.
-	 */
-	public function test_wp_list_sort_preserve_keys( $list, $orderby, $order, $expected ) {
-		$this->assertSame( $expected, wp_list_sort( $list, $orderby, $order, true ) );
-	}
-
 	/**
 	 * @covers WP_List_Util::get_input
 	 */