diff --git a/tests/phpunit/tests/functions/wpListUtil.php b/tests/phpunit/tests/functions/wpListUtil.php
index 45cad6627a..df70b52be4 100644
--- a/tests/phpunit/tests/functions/wpListUtil.php
+++ b/tests/phpunit/tests/functions/wpListUtil.php
@@ -52,4 +52,1092 @@ class Tests_Functions_wpListUtil extends WP_UnitTestCase {
 		$this->assertEqualSets( $expected, $actual );
 		$this->assertEqualSets( $expected, $util->get_output() );
 	}
+
+	/**
+	 * @ticket 55300
+	 *
+	 * @dataProvider data_wp_list_util_pluck
+	 *
+	 * @covers WP_List_Util::pluck
+	 * @covers ::wp_list_pluck
+	 *
+	 * @param array  $target_array The array to create the list from.
+	 * @param string $target_key   The key to pluck.
+	 * @param array  $expected     The expected array.
+	 * @param string $index_key    Optional. Field from the element to use as keys for the new array. Default null.
+	 */
+	public function test_wp_list_util_pluck( $target_array, $target_key, $expected, $index_key = null ) {
+		$util   = new WP_List_Util( $target_array );
+		$actual = $util->pluck( $target_key, $index_key );
+
+		$this->assertEqualSetsWithIndex(
+			$expected,
+			$actual,
+			'The plucked value did not match the expected value.'
+		);
+
+		$this->assertEqualSetsWithIndex(
+			$expected,
+			$util->get_output(),
+			'::get_output() did not return the expected value.'
+		);
+	}
+
+	/**
+	 * Data provider for test_wp_list_util_pluck_simple().
+	 *
+	 * @return array[]
+	 */
+	public function data_wp_list_util_pluck() {
+		return array(
+			'simple'        => array(
+				'target_array' => array(
+					0 => array( 'foo' => 'bar' ),
+				),
+				'target_key'   => 'foo',
+				'expected'     => array( 'bar' ),
+			),
+			'simple_object' => array(
+				'target_array' => array(
+					0 => (object) array( 'foo' => 'bar' ),
+				),
+				'target_key'   => 'foo',
+				'expected'     => array( 'bar' ),
+			),
+		);
+	}
+
+	/**
+	 * @ticket 55300
+	 *
+	 * @covers WP_List_Util::sort
+	 * @covers ::wp_list_sort
+	 */
+	public function test_wp_list_util_sort_simple() {
+		$expected     = array(
+			1 => 'one',
+			2 => 'two',
+			3 => 'three',
+			4 => 'four',
+		);
+		$target_array = array(
+			4 => 'four',
+			2 => 'two',
+			3 => 'three',
+			1 => 'one',
+		);
+
+		$util   = new WP_List_Util( $target_array );
+		$actual = $util->sort();
+
+		$this->assertEqualSets(
+			$expected,
+			$actual,
+			'The sorted value did not match the expected value.'
+		);
+
+		$this->assertEqualSets(
+			$expected,
+			$util->get_output(),
+			'::get_output() did not return the expected value.'
+		);
+	}
+
+	/**
+	 * @ticket 55300
+	 *
+	 * @dataProvider data_wp_list_util_sort_string_arrays
+	 * @dataProvider data_wp_list_util_sort_int_arrays
+	 * @dataProvider data_wp_list_util_sort_arrays_of_arrays
+	 * @dataProvider data_wp_list_util_sort_object_arrays
+	 *
+	 * @covers WP_List_Util::sort
+	 * @covers ::wp_list_sort
+	 *
+	 * @param array  $expected      The expected array.
+	 * @param array  $target_array  The array to create a list from.
+	 * @param array  $orderby       Optional. Either the field name to order by or an array of multiple orderby fields as $orderby => $order.
+	 *                              Default empty array.
+	 * @param string $order         Optional. Either 'ASC' or 'DESC'. Only used if $orderby is a string. Default 'ASC'.
+	 * @param bool   $preserve_keys Optional. Whether to preserve keys. Default false.
+	 */
+	public function test_wp_list_util_sort( $expected, $target_array, $orderby = array(), $order = 'ASC', $preserve_keys = false ) {
+		$util   = new WP_List_Util( $target_array );
+		$actual = $util->sort( $orderby, $order, $preserve_keys );
+
+		$this->assertEqualSetsWithIndex(
+			$expected,
+			$actual,
+			'The sorted value did not match the expected value.'
+		);
+
+		$this->assertEqualSetsWithIndex(
+			$expected,
+			$util->get_output(),
+			'::get_output() did not return the expected value.'
+		);
+	}
+
+	/**
+	 * Data provider that provides string arrays to test_wp_list_util_sort().
+	 *
+	 * @return array[]
+	 */
+	public function data_wp_list_util_sort_string_arrays() {
+		return array(
+			'string[], no keys, no ordering'     => array(
+				'expected'     => array( 'four', 'two', 'three', 'one' ),
+				'target_array' => array( 'four', 'two', 'three', 'one' ),
+			),
+			'string[], int keys, no ordering'    => array(
+				'expected'     => array(
+					4 => 'four',
+					2 => 'two',
+					3 => 'three',
+					1 => 'one',
+				),
+				'target_array' => array(
+					4 => 'four',
+					2 => 'two',
+					3 => 'three',
+					1 => 'one',
+				),
+			),
+			'string[], int keys, $orderby a non-existent field, $order = DESC and $preserve_keys = true' => array(
+				'expected'      => array(
+					4 => 'four',
+					2 => 'two',
+					3 => 'three',
+					1 => 'one',
+				),
+				'target_array'  => array(
+					4 => 'four',
+					2 => 'two',
+					3 => 'three',
+					1 => 'one',
+				),
+				'orderby'       => 'id',
+				'order'         => 'DESC',
+				'preserve_keys' => true,
+			),
+			'string[], string keys, no ordering' => array(
+				'expected'     => array(
+					'four'  => 'four',
+					'two'   => 'two',
+					'three' => 'three',
+					'one'   => 'one',
+				),
+				'target_array' => array(
+					'four'  => 'four',
+					'two'   => 'two',
+					'three' => 'three',
+					'one'   => 'one',
+				),
+			),
+			'string[], string keys, $orderby a non-existent field, $order = DESC and $preserve_keys = true' => array(
+				'expected'      => array(
+					'four'  => 'four',
+					'two'   => 'two',
+					'three' => 'three',
+					'one'   => 'one',
+				),
+				'target_array'  => array(
+					'four'  => 'four',
+					'two'   => 'two',
+					'three' => 'three',
+					'one'   => 'one',
+				),
+				'orderby'       => 'id',
+				'order'         => 'DESC',
+				'preserve_keys' => true,
+			),
+		);
+	}
+
+	/**
+	 * Data provider that provides int arrays for test_wp_list_util_sort().
+	 *
+	 * @return array[]
+	 */
+	public function data_wp_list_util_sort_int_arrays() {
+		return array(
+			'int[], no keys, no ordering'     => array(
+				'expected'     => array( 4, 2, 3, 1 ),
+				'target_array' => array( 4, 2, 3, 1 ),
+			),
+			'int[], int keys, no ordering'    => array(
+				'expected'     => array(
+					4 => 4,
+					2 => 2,
+					3 => 3,
+					1 => 1,
+				),
+				'target_array' => array(
+					4 => 4,
+					2 => 2,
+					3 => 3,
+					1 => 1,
+				),
+			),
+			'int[], int keys, $orderby a non-existent field, $order = DESC and $preserve_keys = true' => array(
+				'expected'      => array(
+					4 => 4,
+					2 => 2,
+					3 => 3,
+					1 => 1,
+				),
+				'target_array'  => array(
+					4 => 4,
+					2 => 2,
+					3 => 3,
+					1 => 1,
+				),
+				'orderby'       => 'id',
+				'order'         => 'DESC',
+				'preserve_keys' => true,
+			),
+			'int[], string keys, no ordering' => array(
+				'expected'     => array(
+					'four'  => 4,
+					'two'   => 2,
+					'three' => 3,
+					'one'   => 1,
+				),
+				'target_array' => array(
+					'four'  => 4,
+					'two'   => 2,
+					'three' => 3,
+					'one'   => 1,
+				),
+			),
+			'int[], string keys, $orderby a non-existent field, $order = DESC and $preserve_keys = true' => array(
+				'expected'      => array(
+					'four'  => 4,
+					'two'   => 2,
+					'three' => 3,
+					'one'   => 1,
+				),
+				'target_array'  => array(
+					'four'  => 4,
+					'two'   => 2,
+					'three' => 3,
+					'one'   => 1,
+				),
+				'orderby'       => 'id',
+				'order'         => 'DESC',
+				'preserve_keys' => true,
+			),
+		);
+	}
+
+	/**
+	 * Data provider that provides arrays of arrays for test_wp_list_util_sort().
+	 *
+	 * @return array[]
+	 */
+	public function data_wp_list_util_sort_arrays_of_arrays() {
+		return array(
+			'array[], no keys, no ordering'     => array(
+				'expected'     => array(
+					array( 'four' ),
+					array( 'two' ),
+					array( 'three' ),
+					array( 'one' ),
+				),
+				'target_array' => array(
+					array( 'four' ),
+					array( 'two' ),
+					array( 'three' ),
+					array( 'one' ),
+				),
+			),
+			'array[], int keys, no ordering'    => array(
+				'expected'     => array(
+					4 => array( 'four' ),
+					2 => array( 'two' ),
+					3 => array( 'three' ),
+					1 => array( 'one' ),
+				),
+				'target_array' => array(
+					4 => array( 'four' ),
+					2 => array( 'two' ),
+					3 => array( 'three' ),
+					1 => array( 'one' ),
+				),
+			),
+			'array[], int keys, $orderby a non-existent field, $order = DESC and $preserve_keys = true' => array(
+				'expected'      => array(
+					4 => array( 'value' => 'four' ),
+					2 => array( 'value' => 'two' ),
+					3 => array( 'value' => 'three' ),
+					1 => array( 'value' => 'one' ),
+				),
+				'target_array'  => array(
+					4 => array( 'value' => 'four' ),
+					2 => array( 'value' => 'two' ),
+					3 => array( 'value' => 'three' ),
+					1 => array( 'value' => 'one' ),
+				),
+				'orderby'       => 'id',
+				'order'         => 'DESC',
+				'preserve_keys' => true,
+			),
+			'array[], int keys, $orderby an existing field, $order = ASC and $preserve_keys = false' => array(
+				'expected'      => array(
+					array(
+						'id'    => 1,
+						'value' => 'one',
+					),
+					array(
+						'id'    => 2,
+						'value' => 'two',
+					),
+					array(
+						'id'    => 3,
+						'value' => 'three',
+					),
+					array(
+						'id'    => 4,
+						'value' => 'four',
+					),
+				),
+				'target_array'  => array(
+					4 => array(
+						'id'    => 4,
+						'value' => 'four',
+					),
+					2 => array(
+						'id'    => 2,
+						'value' => 'two',
+					),
+					3 => array(
+						'id'    => 3,
+						'value' => 'three',
+					),
+					1 => array(
+						'id'    => 1,
+						'value' => 'one',
+					),
+				),
+				'orderby'       => 'id',
+				'order'         => 'ASC',
+				'preserve_keys' => false,
+			),
+			'array[], int keys, $orderby an existing field, $order = DESC and $preserve_keys = true' => array(
+				'expected'      => array(
+					3 => array(
+						'id'    => 4,
+						'value' => 'four',
+					),
+					2 => array(
+						'id'    => 3,
+						'value' => 'three',
+					),
+					1 => array(
+						'id'    => 2,
+						'value' => 'two',
+					),
+					0 => array(
+						'id'    => 1,
+						'value' => 'one',
+					),
+				),
+				'target_array'  => array(
+					array(
+						'id'    => 1,
+						'value' => 'one',
+					),
+					array(
+						'id'    => 2,
+						'value' => 'two',
+					),
+					array(
+						'id'    => 3,
+						'value' => 'three',
+					),
+					array(
+						'id'    => 4,
+						'value' => 'four',
+					),
+				),
+				'orderby'       => 'id',
+				'order'         => 'DESC',
+				'preserve_keys' => true,
+			),
+			'array[], string keys, no ordering' => array(
+				'expected'     => array(
+					'four'  => array( 'value' => 'four' ),
+					'two'   => array( 'value' => 'two' ),
+					'three' => array( 'value' => 'three' ),
+					'one'   => array( 'value' => 'one' ),
+				),
+				'target_array' => array(
+					'four'  => array( 'value' => 'four' ),
+					'two'   => array( 'value' => 'two' ),
+					'three' => array( 'value' => 'three' ),
+					'one'   => array( 'value' => 'one' ),
+				),
+			),
+			'array[], string keys, $orderby a non-existent field, $order = DESC and $preserve_keys = true' => array(
+				'expected'      => array(
+					'four'  => array( 'value' => 'four' ),
+					'two'   => array( 'value' => 'two' ),
+					'three' => array( 'value' => 'three' ),
+					'one'   => array( 'value' => 'one' ),
+				),
+				'target_array'  => array(
+					'four'  => array( 'value' => 'four' ),
+					'two'   => array( 'value' => 'two' ),
+					'three' => array( 'value' => 'three' ),
+					'one'   => array( 'value' => 'one' ),
+				),
+				'orderby'       => 'id',
+				'order'         => 'DESC',
+				'preserve_keys' => true,
+			),
+			'array[], string keys, $orderby an existing field, $order = ASC and $preserve_keys = false' => array(
+				'expected'      => array(
+					array(
+						'id'    => 1,
+						'value' => 'one',
+					),
+					array(
+						'id'    => 2,
+						'value' => 'two',
+					),
+					array(
+						'id'    => 3,
+						'value' => 'three',
+					),
+					array(
+						'id'    => 4,
+						'value' => 'four',
+					),
+				),
+				'target_array'  => array(
+					'four'  => array(
+						'id'    => 4,
+						'value' => 'four',
+					),
+					'two'   => array(
+						'id'    => 2,
+						'value' => 'two',
+					),
+					'three' => array(
+						'id'    => 3,
+						'value' => 'three',
+					),
+					'one'   => array(
+						'id'    => 1,
+						'value' => 'one',
+					),
+				),
+				'orderby'       => 'id',
+				'order'         => 'ASC',
+				'preserve_keys' => false,
+			),
+			'array[], string keys, $orderby an existing field, $order = DESC and $preserve_keys = true' => array(
+				'expected'      => array(
+					'four'  => array(
+						'id'    => 4,
+						'value' => 'four',
+					),
+					'three' => array(
+						'id'    => 3,
+						'value' => 'three',
+					),
+					'two'   => array(
+						'id'    => 2,
+						'value' => 'two',
+					),
+					'one'   => array(
+						'id'    => 1,
+						'value' => 'one',
+					),
+				),
+				'target_array'  => array(
+					'one'   => array(
+						'id'    => 1,
+						'value' => 'one',
+					),
+					'two'   => array(
+						'id'    => 2,
+						'value' => 'two',
+					),
+					'three' => array(
+						'id'    => 3,
+						'value' => 'three',
+					),
+					'four'  => array(
+						'id'    => 4,
+						'value' => 'four',
+					),
+				),
+				'orderby'       => 'id',
+				'order'         => 'DESC',
+				'preserve_keys' => true,
+			),
+			'array[], string keys, $orderby an existing field, $order = asc (lowercase) and $preserve_keys = false' => array(
+				'expected'      => array(
+					array(
+						'id'    => 1,
+						'value' => 'one',
+					),
+					array(
+						'id'    => 2,
+						'value' => 'two',
+					),
+					array(
+						'id'    => 3,
+						'value' => 'three',
+					),
+					array(
+						'id'    => 4,
+						'value' => 'four',
+					),
+				),
+				'target_array'  => array(
+					'four'  => array(
+						'id'    => 4,
+						'value' => 'four',
+					),
+					'two'   => array(
+						'id'    => 2,
+						'value' => 'two',
+					),
+					'three' => array(
+						'id'    => 3,
+						'value' => 'three',
+					),
+					'one'   => array(
+						'id'    => 1,
+						'value' => 'one',
+					),
+				),
+				'orderby'       => 'id',
+				'order'         => 'asc',
+				'preserve_keys' => false,
+			),
+			'array[], string keys, $orderby an existing field, no order and $preserve_keys = false' => array(
+				'expected'      => array(
+					'four'  => array(
+						'id'    => 4,
+						'value' => 'four',
+					),
+					'three' => array(
+						'id'    => 3,
+						'value' => 'three',
+					),
+					'two'   => array(
+						'id'    => 2,
+						'value' => 'two',
+					),
+					'one'   => array(
+						'id'    => 1,
+						'value' => 'one',
+					),
+				),
+				'target_array'  => array(
+					'one'   => array(
+						'id'    => 1,
+						'value' => 'one',
+					),
+					'two'   => array(
+						'id'    => 2,
+						'value' => 'two',
+					),
+					'three' => array(
+						'id'    => 3,
+						'value' => 'three',
+					),
+					'four'  => array(
+						'id'    => 4,
+						'value' => 'four',
+					),
+				),
+				'orderby'       => array( 'id' ),
+				'order'         => null,
+				'preserve_keys' => true,
+			),
+			'array[], string keys, $orderby two existing fields, differing orders and $preserve_keys = false' => array(
+				'expected'      => array(
+					array(
+						'id'    => 1,
+						'value' => 'one',
+					),
+					array(
+						'id'    => 2,
+						'value' => 'two',
+					),
+					array(
+						'id'    => 3,
+						'value' => 'three',
+					),
+					array(
+						'id'    => 4,
+						'value' => 'four',
+					),
+				),
+				'target_array'  => array(
+					'four'  => array(
+						'id'    => 4,
+						'value' => 'four',
+					),
+					'two'   => array(
+						'id'    => 2,
+						'value' => 'two',
+					),
+					'three' => array(
+						'id'    => 3,
+						'value' => 'three',
+					),
+					'one'   => array(
+						'id'    => 1,
+						'value' => 'one',
+					),
+				),
+				'orderby'       => array(
+					'id'    => 'asc',
+					'value' => 'DESC',
+				),
+				'order'         => null,
+				'preserve_keys' => false,
+			),
+		);
+	}
+
+	/**
+	 * Data provider that provides object arrays for test_wp_list_util_sort().
+	 *
+	 * @return array[]
+	 */
+	public function data_wp_list_util_sort_object_arrays() {
+		return array(
+			'object[], no keys, no ordering'     => array(
+				'expected'     => array(
+					(object) array( 'four' ),
+					(object) array( 'two' ),
+					(object) array( 'three' ),
+					(object) array( 'one' ),
+				),
+				'target_array' => array(
+					(object) array( 'four' ),
+					(object) array( 'two' ),
+					(object) array( 'three' ),
+					(object) array( 'one' ),
+				),
+			),
+			'object[], int keys, no ordering'    => array(
+				'expected'     => array(
+					4 => (object) array( 'four' ),
+					2 => (object) array( 'two' ),
+					3 => (object) array( 'three' ),
+					1 => (object) array( 'one' ),
+				),
+				'target_array' => array(
+					4 => (object) array( 'four' ),
+					2 => (object) array( 'two' ),
+					3 => (object) array( 'three' ),
+					1 => (object) array( 'one' ),
+				),
+			),
+			'object[], int keys, $orderby an existing field, $order = ASC and $preserve_keys = false' => array(
+				'expected'      => array(
+					(object) array(
+						'id'    => 1,
+						'value' => 'one',
+					),
+					(object) array(
+						'id'    => 2,
+						'value' => 'two',
+					),
+					(object) array(
+						'id'    => 3,
+						'value' => 'three',
+					),
+					(object) array(
+						'id'    => 4,
+						'value' => 'four',
+					),
+				),
+				'target_array'  => array(
+					4 => (object) array(
+						'id'    => 4,
+						'value' => 'four',
+					),
+					2 => (object) array(
+						'id'    => 2,
+						'value' => 'two',
+					),
+					3 => (object) array(
+						'id'    => 3,
+						'value' => 'three',
+					),
+					1 => (object) array(
+						'id'    => 1,
+						'value' => 'one',
+					),
+				),
+				'orderby'       => 'id',
+				'order'         => 'ASC',
+				'preserve_keys' => false,
+			),
+			'object[], int keys, $orderby an existing field, $order = DESC and $preserve_keys = true' => array(
+				'expected'      => array(
+					3 => (object) array(
+						'id'    => 4,
+						'value' => 'four',
+					),
+					2 => (object) array(
+						'id'    => 3,
+						'value' => 'three',
+					),
+					1 => (object) array(
+						'id'    => 2,
+						'value' => 'two',
+					),
+					0 => (object) array(
+						'id'    => 1,
+						'value' => 'one',
+					),
+				),
+				'target_array'  => array(
+					(object) array(
+						'id'    => 1,
+						'value' => 'one',
+					),
+					(object) array(
+						'id'    => 2,
+						'value' => 'two',
+					),
+					(object) array(
+						'id'    => 3,
+						'value' => 'three',
+					),
+					(object) array(
+						'id'    => 4,
+						'value' => 'four',
+					),
+				),
+				'orderby'       => 'id',
+				'order'         => 'DESC',
+				'preserve_keys' => true,
+			),
+			'object[], string keys, no ordering' => array(
+				'expected'     => array(
+					'four'  => (object) array( 'value' => 'four' ),
+					'two'   => (object) array( 'value' => 'two' ),
+					'three' => (object) array( 'value' => 'three' ),
+					'one'   => (object) array( 'value' => 'one' ),
+				),
+				'target_array' => array(
+					'four'  => (object) array( 'value' => 'four' ),
+					'two'   => (object) array( 'value' => 'two' ),
+					'three' => (object) array( 'value' => 'three' ),
+					'one'   => (object) array( 'value' => 'one' ),
+				),
+			),
+			'object[], string keys, $orderby a non-existent field, $order = DESC and $preserve_keys = true' => array(
+				'expected'      => array(
+					'four'  => (object) array( 'value' => 'four' ),
+					'two'   => (object) array( 'value' => 'two' ),
+					'three' => (object) array( 'value' => 'three' ),
+					'one'   => (object) array( 'value' => 'one' ),
+				),
+				'target_array'  => array(
+					'four'  => (object) array( 'value' => 'four' ),
+					'two'   => (object) array( 'value' => 'two' ),
+					'three' => (object) array( 'value' => 'three' ),
+					'one'   => (object) array( 'value' => 'one' ),
+				),
+				'orderby'       => 'id',
+				'order'         => 'DESC',
+				'preserve_keys' => true,
+			),
+			'object[], string keys, $orderby an existing field, $order = ASC and $preserve_keys = false' => array(
+				'expected'      => array(
+					(object) array(
+						'id'    => 1,
+						'value' => 'one',
+					),
+					(object) array(
+						'id'    => 2,
+						'value' => 'two',
+					),
+					(object) array(
+						'id'    => 3,
+						'value' => 'three',
+					),
+					(object) array(
+						'id'    => 4,
+						'value' => 'four',
+					),
+				),
+				'target_array'  => array(
+					'four'  => (object) array(
+						'id'    => 4,
+						'value' => 'four',
+					),
+					'two'   => (object) array(
+						'id'    => 2,
+						'value' => 'two',
+					),
+					'three' => (object) array(
+						'id'    => 3,
+						'value' => 'three',
+					),
+					'one'   => (object) array(
+						'id'    => 1,
+						'value' => 'one',
+					),
+				),
+				'orderby'       => 'id',
+				'order'         => 'ASC',
+				'preserve_keys' => false,
+			),
+			'object[], string keys, $orderby an existing field, $order = DESC and $preserve_keys = true' => array(
+				'expected'      => array(
+					'four'  => (object) array(
+						'id'    => 4,
+						'value' => 'four',
+					),
+					'three' => (object) array(
+						'id'    => 3,
+						'value' => 'three',
+					),
+					'two'   => (object) array(
+						'id'    => 2,
+						'value' => 'two',
+					),
+					'one'   => (object) array(
+						'id'    => 1,
+						'value' => 'one',
+					),
+				),
+				'target_array'  => array(
+					'one'   => (object) array(
+						'id'    => 1,
+						'value' => 'one',
+					),
+					'two'   => (object) array(
+						'id'    => 2,
+						'value' => 'two',
+					),
+					'three' => (object) array(
+						'id'    => 3,
+						'value' => 'three',
+					),
+					'four'  => (object) array(
+						'id'    => 4,
+						'value' => 'four',
+					),
+				),
+				'orderby'       => 'id',
+				'order'         => 'DESC',
+				'preserve_keys' => true,
+			),
+		);
+	}
+
+	/**
+	 * Tests non-existent '$orderby' fields.
+	 *
+	 * In PHP < 7.0.0, the sorting behaviour is different, which Core does not
+	 * currently handle. Until this is fixed, or the minimum PHP version is
+	 * raised to PHP 7.0.0+, these tests will be skipped on PHP < 7.0.0.
+	 *
+	 * @ticket 55300
+	 *
+	 * @dataProvider data_wp_list_util_sort_php_7_or_greater
+	 *
+	 * @covers WP_List_Util::sort
+	 * @covers ::wp_list_sort
+	 *
+	 * @param array  $expected      The expected array.
+	 * @param array  $target_array  The array to create a list from.
+	 * @param array  $orderby       Optional. Either the field name to order by or an array of multiple orderby fields as $orderby => $order.
+	 *                              Default empty array.
+	 * @param string $order         Optional. Either 'ASC' or 'DESC'. Only used if $orderby is a string. Default 'ASC'.
+	 * @param bool   $preserve_keys Optional. Whether to preserve keys. Default false.
+	 */
+	public function test_wp_list_util_sort_php_7_or_greater( $expected, $target_array, $orderby = array(), $order = 'ASC', $preserve_keys = false ) {
+		if ( version_compare( PHP_VERSION, '7.0.0', '<' ) ) {
+			$this->markTestSkipped( 'This test can only run on PHP 7.0 or greater due to an unstable sort order.' );
+		}
+
+		$util   = new WP_List_Util( $target_array );
+		$actual = $util->sort( $orderby, $order, $preserve_keys );
+
+		$this->assertEqualSetsWithIndex(
+			$expected,
+			$actual,
+			'The sorted value did not match the expected value.'
+		);
+		$this->assertEqualSetsWithIndex(
+			$expected,
+			$util->get_output(),
+			'::get_output() did not return the expected value.'
+		);
+	}
+
+	/**
+	 * Data provider for test_wp_list_util_sort_php_7_or_greater().
+	 *
+	 * @return array[]
+	 */
+	public function data_wp_list_util_sort_php_7_or_greater() {
+		return array(
+			'int[], int keys, $orderby a non-existent field, $order = ASC and $preserve_keys = false' => array(
+				'expected'      => array( 4, 2, 3, 1 ),
+				'target_array'  => array(
+					4 => 4,
+					2 => 2,
+					3 => 3,
+					1 => 1,
+				),
+				'orderby'       => 'id',
+				'order'         => 'ASC',
+				'preserve_keys' => false,
+			),
+			'int[], string keys, $orderby a non-existent field, $order = ASC and $preserve_keys = false' => array(
+				'expected'      => array( 4, 2, 3, 1 ),
+				'target_array'  => array(
+					'four'  => 4,
+					'two'   => 2,
+					'three' => 3,
+					'one'   => 1,
+				),
+				'orderby'       => 'id',
+				'order'         => 'ASC',
+				'preserve_keys' => false,
+			),
+			'string[], int keys, $orderby a non-existent field, $order = ASC and $preserve_keys = false' => array(
+				'expected'      => array( 'four', 'two', 'three', 'one' ),
+				'target_array'  => array(
+					4 => 'four',
+					2 => 'two',
+					3 => 'three',
+					1 => 'one',
+				),
+				'orderby'       => 'id',
+				'order'         => 'ASC',
+				'preserve_keys' => false,
+			),
+			'string[], string keys, $orderby a non-existent field, $order = ASC and $preserve_keys = false' => array(
+				'expected'      => array( 'four', 'two', 'three', 'one' ),
+				'target_array'  => array(
+					'four'  => 'four',
+					'two'   => 'two',
+					'three' => 'three',
+					'one'   => 'one',
+				),
+				'orderby'       => 'id',
+				'order'         => 'ASC',
+				'preserve_keys' => false,
+			),
+			'array[], int keys, $orderby a non-existent field, $order = ASC and $preserve_keys = false' => array(
+				'expected'      => array(
+					array( 'value' => 'four' ),
+					array( 'value' => 'two' ),
+					array( 'value' => 'three' ),
+					array( 'value' => 'one' ),
+				),
+				'target_array'  => array(
+					4 => array( 'value' => 'four' ),
+					2 => array( 'value' => 'two' ),
+					3 => array( 'value' => 'three' ),
+					1 => array( 'value' => 'one' ),
+				),
+				'orderby'       => 'id',
+				'order'         => 'ASC',
+				'preserve_keys' => false,
+			),
+			'array[], string keys, $orderby a non-existent field, $order = ASC and $preserve_keys = false' => array(
+				'expected'      => array(
+					array( 'value' => 'four' ),
+					array( 'value' => 'two' ),
+					array( 'value' => 'three' ),
+					array( 'value' => 'one' ),
+				),
+				'target_array'  => array(
+					'four'  => array( 'value' => 'four' ),
+					'two'   => array( 'value' => 'two' ),
+					'three' => array( 'value' => 'three' ),
+					'one'   => array( 'value' => 'one' ),
+				),
+				'orderby'       => 'id',
+				'order'         => 'ASC',
+				'preserve_keys' => false,
+			),
+			'object[], int keys, $orderby a non-existent field, $order = ASC and $preserve_keys = false' => array(
+				'expected'      => array(
+					(object) array( 'value' => 'four' ),
+					(object) array( 'value' => 'two' ),
+					(object) array( 'value' => 'three' ),
+					(object) array( 'value' => 'one' ),
+				),
+				'target_array'  => array(
+					4 => (object) array( 'value' => 'four' ),
+					2 => (object) array( 'value' => 'two' ),
+					3 => (object) array( 'value' => 'three' ),
+					1 => (object) array( 'value' => 'one' ),
+				),
+				'orderby'       => 'id',
+				'order'         => 'ASC',
+				'preserve_keys' => false,
+			),
+			'object[], int keys, $orderby a non-existent field, $order = DESC and $preserve_keys = true' => array(
+				'expected'      => array(
+					4 => (object) array( 'value' => 'four' ),
+					2 => (object) array( 'value' => 'two' ),
+					3 => (object) array( 'value' => 'three' ),
+					1 => (object) array( 'value' => 'one' ),
+				),
+				'target_array'  => array(
+					4 => (object) array( 'value' => 'four' ),
+					2 => (object) array( 'value' => 'two' ),
+					3 => (object) array( 'value' => 'three' ),
+					1 => (object) array( 'value' => 'one' ),
+				),
+				'orderby'       => 'id',
+				'order'         => 'DESC',
+				'preserve_keys' => true,
+			),
+			'object[], string keys, $orderby a non-existent field, $order = ASC and $preserve_keys = false' => array(
+				'expected'      => array(
+					(object) array( 'value' => 'four' ),
+					(object) array( 'value' => 'two' ),
+					(object) array( 'value' => 'three' ),
+					(object) array( 'value' => 'one' ),
+				),
+				'target_array'  => array(
+					'four'  => (object) array( 'value' => 'four' ),
+					'two'   => (object) array( 'value' => 'two' ),
+					'three' => (object) array( 'value' => 'three' ),
+					'one'   => (object) array( 'value' => 'one' ),
+				),
+				'orderby'       => 'id',
+				'order'         => 'ASC',
+				'preserve_keys' => false,
+			),
+			'object[], string keys, $orderby a non-existent field, $order = DESC and $preserve_keys = true' => array(
+				'expected'      => array(
+					'four'  => (object) array( 'value' => 'four' ),
+					'two'   => (object) array( 'value' => 'two' ),
+					'three' => (object) array( 'value' => 'three' ),
+					'one'   => (object) array( 'value' => 'one' ),
+				),
+				'target_array'  => array(
+					'four'  => (object) array( 'value' => 'four' ),
+					'two'   => (object) array( 'value' => 'two' ),
+					'three' => (object) array( 'value' => 'three' ),
+					'one'   => (object) array( 'value' => 'one' ),
+				),
+				'orderby'       => 'id',
+				'order'         => 'DESC',
+				'preserve_keys' => true,
+			),
+		);
+	}
+
 }