diff --git a/.travis.yml b/.travis.yml
index b84ca7c..fefe759 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -2,10 +2,6 @@ language: php
 
 matrix:
   include:
-    - php: 5.3
-      env: WP_VERSION=4.3.3 ES_VERSION=2.2.0
-    - php: 5.3
-      env: WP_VERSION=latest ES_VERSION=2.2.0
     - php: 5.6
       env: WP_VERSION=latest ES_VERSION=2.2.0
     - php: 7.0
@@ -27,6 +23,13 @@ before_install:
     - sudo service elasticsearch start
 
 before_script:
+    - export PATH="$HOME/.composer/vendor/bin:$PATH"
+    - |
+      if [[ ${TRAVIS_PHP_VERSION:0:2} == "7." ]]; then
+        composer global require "phpunit/phpunit=5.7.*"
+      else
+        composer global require "phpunit/phpunit=4.8.*"
+      fi
     - bash bin/install-wp-tests.sh wordpress_test root '' localhost $WP_VERSION
     - sleep 5 # ensure ES is running
 
diff --git a/adapters/searchpress.php b/adapters/searchpress.php
index 0f2b5fb..3633d89 100644
--- a/adapters/searchpress.php
+++ b/adapters/searchpress.php
@@ -11,6 +11,7 @@ protected function query_es( $es_args ) {
 
 function sp_es_field_map( $es_map ) {
 	return wp_parse_args( array(
+		'ID'                    => 'post_id',
 		'post_name'             => 'post_name.raw',
 		'post_title'            => 'post_title.raw',
 		'post_title.analyzed'   => 'post_title',
@@ -74,4 +75,4 @@ function es_wp_query_index_test_data() {
 		SP_API()->post( '_refresh' );
 	}
 
-}
\ No newline at end of file
+}
diff --git a/adapters/travis.php b/adapters/travis.php
index 7c66213..07dc6d9 100644
--- a/adapters/travis.php
+++ b/adapters/travis.php
@@ -13,6 +13,7 @@ protected function query_es( $es_args ) {
 
 function travis_es_field_map( $es_map ) {
 	return wp_parse_args( array(
+		'ID'                => 'post_id',
 		'post_meta'         => 'post_meta.%s.value',
 		'post_author'       => 'post_author.user_id',
 		'post_date'         => 'post_date.date',
diff --git a/adapters/wpcom-vip.php b/adapters/wpcom-vip.php
index f012bb3..e88ff28 100644
--- a/adapters/wpcom-vip.php
+++ b/adapters/wpcom-vip.php
@@ -20,6 +20,8 @@ protected function set_posts( $q, $es_response ) {
 						$post_id = (array) $hit['fields'][ $this->es_map( 'post_id' ) ];
 						$this->posts[] = reset( $post_id );
 					}
+
+					$this->posts = $this->post_query_sort_handler( $this->posts, $q );
 					return;
 
 				case 'id=>parent' :
@@ -33,7 +35,6 @@ protected function set_posts( $q, $es_response ) {
 				default :
 					if ( apply_filters( 'es_query_use_source', false ) ) {
 						$this->posts = wp_list_pluck( $es_response['results']['hits'], '_source' );
-						return;
 					} else {
 						$post_ids = array();
 						foreach ( $es_response['results']['hits'] as $hit ) {
@@ -46,8 +47,10 @@ protected function set_posts( $q, $es_response ) {
 							$post__in = implode( ',', $post_ids );
 							$this->posts = $wpdb->get_results( "SELECT $wpdb->posts.* FROM $wpdb->posts WHERE ID IN ($post__in) ORDER BY FIELD( {$wpdb->posts}.ID, $post__in )" );
 						}
-						return;
 					}
+
+					$this->posts = $this->post_query_sort_handler( $this->posts, $q );
+					return;
 			}
 		} else {
 			$this->posts = array();
@@ -73,6 +76,7 @@ public function set_found_posts( $q, $es_response ) {
 
 function vip_es_field_map( $es_map ) {
 	return wp_parse_args( array(
+		'ID'                            => 'post_id',
 		'post_author'                   => 'author_id',
 		'post_author.user_nicename'     => 'author_login',
 		'post_date'                     => 'date',
@@ -100,8 +104,8 @@ function vip_es_field_map( $es_map ) {
 		'post_title'                    => 'title',
 		'post_title.analyzed'           => 'title',
 		'post_excerpt'                  => 'excerpt',
-		'post_password'                 => 'post_password',  // this isn't indexed on vip
-		'post_name'                     => 'post_name',      // this isn't indexed on vip
+		'post_password'                 => 'post_password', // this isn't indexed on vip
+		'post_name'                     => 'slug',
 		'post_modified'                 => 'modified',
 		'post_modified.year'            => 'modified_token.year',
 		'post_modified.month'           => 'modified_token.month',
@@ -123,9 +127,9 @@ function vip_es_field_map( $es_map ) {
 		'post_modified_gmt.minute'      => 'modified_gmt_token.minute',
 		'post_modified_gmt.second'      => 'modified_gmt_token.second',
 		'post_parent'                   => 'parent_post_id',
-		'menu_order'                    => 'menu_order',     // this isn't indexed on vip
+		'menu_order'                    => 'menu_order',
 		'post_mime_type'                => 'post_mime_type', // this isn't indexed on vip
-		'comment_count'                 => 'comment_count',  // this isn't indexed on vip
+		'comment_count'                 => 'discussion.comment_count',
 		'post_meta'                     => 'meta.%s.value.raw_lc',
 		'post_meta.analyzed'            => 'meta.%s.value',
 		'post_meta.long'                => 'meta.%s.long',
diff --git a/class-es-wp-query-shoehorn.php b/class-es-wp-query-shoehorn.php
index 3d7c938..6818570 100644
--- a/class-es-wp-query-shoehorn.php
+++ b/class-es-wp-query-shoehorn.php
@@ -219,4 +219,4 @@ private function reboot_query_vars( &$query ) {
 			$q['posts_per_page'] = get_option( 'posts_per_page' );
 		}
 	}
-}
\ No newline at end of file
+}
diff --git a/class-es-wp-query-wrapper.php b/class-es-wp-query-wrapper.php
index 5c64f0a..a35a417 100644
--- a/class-es-wp-query-wrapper.php
+++ b/class-es-wp-query-wrapper.php
@@ -47,6 +47,8 @@ protected function set_posts( $q, $es_response ) {
 						$post_id = (array) $hit['fields'][ $this->es_map( 'post_id' ) ];
 						$this->posts[] = reset( $post_id );
 					}
+
+					$this->posts = $this->post_query_sort_handler( $this->posts, $q );
 					return;
 
 				case 'id=>parent' :
@@ -60,7 +62,6 @@ protected function set_posts( $q, $es_response ) {
 				default :
 					if ( apply_filters( 'es_query_use_source', false ) ) {
 						$this->posts = wp_list_pluck( $es_response['hits']['hits'], '_source' );
-						return;
 					} else {
 						$post_ids = array();
 						foreach ( $es_response['hits']['hits'] as $hit ) {
@@ -73,14 +74,88 @@ protected function set_posts( $q, $es_response ) {
 							$post__in = implode( ',', $post_ids );
 							$this->posts = $wpdb->get_results( "SELECT $wpdb->posts.* FROM $wpdb->posts WHERE ID IN ($post__in) ORDER BY FIELD( {$wpdb->posts}.ID, $post__in )" );
 						}
-						return;
 					}
+
+					$this->posts = $this->post_query_sort_handler( $this->posts, $q );
 			}
 		} else {
 			$this->posts = array();
 		}
 	}
 
+	/**
+	 * Post query sort handler
+	 * Handle sorting by `post__in`, `post__in` and `post_parent__in`.
+	 *
+	 * @param  array $posts Query result posts.
+	 * @param  array $query Initial query.
+	 * @return array Sorted posts.
+	 */
+	protected function post_query_sort_handler( $posts, $query ) {
+		if ( empty( $query['orderby'] ) ) {
+			return $posts;
+		}
+
+		// Determine the key to sort by.
+		switch ( $query['orderby'] ) {
+			case 'post__in' :
+				$key = 'ID';
+				break;
+
+			case 'post_name__in' :
+				$key = 'post_name';
+				break;
+
+			case 'post_parent__in' :
+				$key = 'post_parent';
+				break;
+
+			default :
+				return $posts;
+		}
+
+		// Flip the order to allow retrieval by index.
+		$order = array_flip( $query[ $query['orderby'] ] );
+
+		// Support raw Elasticsearch documents.
+		$use_source = apply_filters( 'es_query_use_source', false );
+		if ( $use_source ) {
+			$key = $this->es_map( $key );
+		}
+
+		usort( $posts, function( $a, $b ) use ( $order, $key, $use_source ) {
+			// Add support for using the Elasticsearch _source field.
+			if ( $use_source ) {
+				// Cast the array to object to mock the `WP_Post` object.
+				$a = (object) $a;
+				$b = (object) $b;
+			} else {
+				// Add support for a query of only post ID fields.
+				if ( ! ( $a instanceof WP_Post ) ) {
+					$a = get_post( $a );
+				}
+
+				if ( ! ( $b instanceof WP_Post ) ) {
+					$b = get_post( $b );
+				}
+			}
+
+			if (
+				! isset( $a->$key ) || ! isset( $b->$key )
+				|| ! isset( $order[ $a->$key ] ) || ! isset( $order[ $b->$key ] ) ) {
+				return 0;
+			}
+
+			if ( $order[ $a->$key ] === $order[ $b->$key ] ) {
+				return 0;
+			} else {
+				return $order[ $a->$key ] < $order[ $b->$key ] ? -1 : 1;
+			}
+		} );
+
+		return $posts;
+	}
+
 	// @todo: Core queries where 1=0 here, which probably happens for good reason.
 	// We're just going to abandon ship for now, but if it causes issues we'll switch
 	// to a mysql query where 1=0
@@ -462,6 +537,9 @@ public function get_posts() {
 			$q['attachment'] = sanitize_title_for_query( wp_basename( $q['attachment'] ) );
 			$q['name'] = $q['attachment'];
 			$filter[] = $this->dsl_terms( $this->es_map( 'post_name' ), $q['attachment'] );
+		} elseif ( ! empty( $q['post_name__in'] ) ) {
+			$post_name__in = $q['post_name__in'];
+			$filter[] = $this->dsl_terms( $this->es_map( 'post_name' ), $post_name__in );
 		}
 
 
@@ -682,12 +760,8 @@ public function get_posts() {
 			}
 		} elseif ( 'none' == $q['orderby'] ) {
 			// nothing to see here
-		} elseif ( $q['orderby'] == 'post__in' && ! empty( $post__in ) ) {
-			// @todo: Figure this out... Elasticsearch doesn't have an equivalent of this
-			// $orderby = "FIELD( {$wpdb->posts}.ID, $post__in )";
-		} elseif ( $q['orderby'] == 'post_parent__in' && ! empty( $post_parent__in ) ) {
-			// (see above)
-			// $orderby = "FIELD( {$wpdb->posts}.post_parent, $post_parent__in )";
+		} elseif ( in_array( $q['orderby'], array( 'post__in', 'post_parent__in', 'post_name__in' ) ) ) {
+			// Handled post-query by `ES_WP_Query_Wrapper::post_query_sort_handler()`.
 		} else {
 			if ( is_array( $q['orderby'] ) ) {
 				foreach ( $q['orderby'] as $_orderby => $order ) {
diff --git a/tests/query/query.php b/tests/query/query.php
index d51f4bd..0164808 100644
--- a/tests/query/query.php
+++ b/tests/query/query.php
@@ -67,4 +67,147 @@ function test_orderby() {
 		$q5 = new ES_WP_Query( array( 'orderby' => array() ) );
 		$this->assertFalse( isset( $q5->es_args['sort'] ) );
 	}
+
+	function test_orderby_post__in() {
+		$p_a = $this->factory->post->create();
+		$p_b = $this->factory->post->create();
+		$p_c = $this->factory->post->create();
+		$p_d = $this->factory->post->create();
+		es_wp_query_index_test_data();
+
+		$post__in = [
+			$p_c,
+			$p_a,
+			$p_d,
+			$p_b,
+		];
+
+		$q = new ES_WP_Query( [
+			'post__in' => $post__in,
+			'orderby' => 'post__in',
+			'order' => 'ASC',
+			'posts_per_page' => 4,
+		] );
+
+		$this->assertNotEmpty( $q->posts );
+
+		// Verify that the post is in the proper array.
+		foreach ( $q->posts as $post ) {
+			$this->assertTrue( in_array( $post->ID, $post__in, true ) );
+		}
+
+		// Assert that the order matches
+		foreach ( $post__in as $i => $post_ID ) {
+			$this->assertEquals(
+				$post_ID,
+				$q->posts[ $i ]->ID,
+				'Post not in expected order from `post__in`.'
+			);
+		}
+
+		// Query only the ID field.
+		$q2 = new ES_WP_Query( [
+			'post__in' => $post__in,
+			'orderby' => 'post__in',
+			'order' => 'ASC',
+			'posts_per_page' => 4,
+			'fields' => 'ids',
+		] );
+
+		$this->assertNotEmpty( $q2->posts );
+
+		// Verify that the post is in the proper array.
+		foreach ( $q2->posts as $post ) {
+			$this->assertTrue( in_array( $post, $post__in, true ) );
+		}
+
+		// Assert that the order matches
+		foreach ( $post__in as $i => $post_ID ) {
+			$this->assertEquals(
+				$post_ID,
+				$q2->posts[ $i ],
+				'Post not in expected order from `post__in`.'
+			);
+		}
+	}
+
+	function test_post_name__in() {
+		$post_a = $this->factory->post->create( [ 'post_name' => 'post-a' ] );
+		$post_b = $this->factory->post->create( [ 'post_name' => 'post-b' ] );
+		$post_c = $this->factory->post->create( [ 'post_name' => 'post-c' ] );
+		es_wp_query_index_test_data();
+
+		$post_name__in = [
+			'post-c',
+			'post-a',
+			'post-b',
+		];
+
+		$q = new ES_WP_Query( [
+			'post_name__in' => $post_name__in,
+			'orderby' => 'post_name__in',
+			'order' => 'ASC',
+		] );
+
+		$this->assertNotEmpty( $q->posts );
+
+		// Verify that the post name is in the proper array.
+		foreach ( $q->posts as $post ) {
+			$this->assertTrue( in_array( $post->post_name, $post_name__in, true ) );
+		}
+
+		// Assert that the order matches.
+		foreach ( $post_name__in as $i => $post_name ) {
+			$this->assertEquals(
+				$post_name,
+				$q->posts[ $i ]->post_name,
+				'Post not in expected order from `post_name__in`.'
+			);
+		}
+	}
+
+	public function test_post_parent__in() {
+		$parent_a = $this->factory->post->create();
+		$parent_b = $this->factory->post->create();
+		$parent_c = $this->factory->post->create();
+		$children = [];
+
+		foreach( [ $parent_a, $parent_b, $parent_c ] as $parent ) {
+			$children[ $parent ] = $this->factory->post->create( [ 'post_parent' => $parent ] );
+		}
+
+		es_wp_query_index_test_data();
+
+		$post_parent__in = [
+			$parent_b,
+			$parent_a,
+			$parent_c,
+		];
+
+		$q = new ES_WP_Query( [
+			'post_parent__in' => $post_parent__in,
+			'orderby' => 'post_parent__in',
+			'order' => 'ASC',
+		] );
+
+		$this->assertNotEmpty( $q->posts );
+
+		// Verify that the post is in the proper children array.
+		foreach ( $q->posts as $post ) {
+			$this->assertEquals(
+				$post->ID,
+				$children[ $post->post_parent ],
+				'Unexpected post returned from `post_parent__in`.'
+			);
+		}
+
+		// Verify the order of `post_parent__in`.
+		foreach ( $post_parent__in as $i => $post_parent_id ) {
+			$this->assertEquals(
+				$post_parent_id,
+				$q->posts[ $i ]->post_parent,
+				'Post not in expected order from `post_parent__in`.'
+			);
+		}
+	}
 }