diff --git a/tests/phpunit/tests/query/results.php b/tests/phpunit/tests/query/results.php
index 53a23f2669..bcff83916b 100644
--- a/tests/phpunit/tests/query/results.php
+++ b/tests/phpunit/tests/query/results.php
@@ -365,6 +365,23 @@ class Tests_Query_Results extends WP_UnitTestCase {
 		), wp_list_pluck( $posts, 'post_title' ) );
 	}
 
+	/**
+	 * @ticket 39055
+	 */
+	function test_query_orderby_post_parent__in_with_order_desc() {
+		$post_parent__in_array = array( self::$parent_two, self::$parent_one );
+		$expected_returned_array = array( 'child-three', 'child-four', 'child-one', 'child-two' );
+
+		$posts = $this->q->query( array(
+			'post_parent__in' => $post_parent__in_array,
+			'orderby'         => 'post_parent__in',
+			'order'           => 'desc',
+		) );
+
+		// order=desc does not influence the order of returned results (returns same order as order=asc)
+		$this->assertEquals( $expected_returned_array, wp_list_pluck( $posts, 'post_title' ) );
+	}
+
 	/**
 	 * @ticket 39055
 	 */
@@ -419,6 +436,37 @@ class Tests_Query_Results extends WP_UnitTestCase {
 		$this->assertSame( $expected_returned_array, $q->posts );
 	}
 
+	/**
+	 * @ticket 39055
+	 */
+	function test_query_orderby_post_name__in_with_order_asc() {
+		$post_name__in_array = array( 'parent-two', 'parent-one', 'parent-three' );
+
+		$q = new WP_Query( array(
+			'post_name__in' => $post_name__in_array,
+			'orderby'       => 'post_name__in',
+			'order'         => 'asc'
+		) );
+
+		$this->assertSame( $post_name__in_array, array_unique( wp_list_pluck( $q->posts, 'post_title' ) ) );
+	}
+
+	/**
+	 * @ticket 39055
+	 */
+	function test_query_orderby_post_name__in_with_order_desc() {
+		$post_name__in_array = array( 'parent-two', 'parent-one', 'parent-three' );
+
+		$q = new WP_Query( array(
+			'post_name__in' => $post_name__in_array,
+			'orderby'       => 'post_name__in',
+			'order'         => 'desc'
+		) );
+
+		// order=desc does not influence the order of returned results (returns same order as order=asc)
+		$this->assertSame( $post_name__in_array, array_unique( wp_list_pluck( $q->posts, 'post_title' ) ) );
+	}
+
 	/**
 	 * @ticket 27252
 	 * @ticket 31194