Index: tests/phpunit/tests/comment/query.php
===================================================================
--- tests/phpunit/tests/comment/query.php	(revision 29854)
+++ tests/phpunit/tests/comment/query.php	(working copy)
@@ -270,4 +270,50 @@
 
 		$this->assertEqualSets( array( $c3 ), $comment_ids );
 	}
+	
+	/**
+	 * @ticket 29885
+	 */
+	function test_fields_post_author__in() {
+		$author_id1 = 105;
+		$author_id2 = 106;
+		
+		$p1 = $this->factory->post->create( array( 'post_author' => $author_id1	) );
+		$p2 = $this->factory->post->create( array( 'post_author' => $author_id1	) );
+		$p3 = $this->factory->post->create( array( 'post_author' => $author_id2	) );
+		
+		$c1 = $this->factory->comment->create( array( 'comment_post_ID' => $p1, 'user_id' => 1, 'comment_approved' => '1' ) );
+		$c2 = $this->factory->comment->create( array( 'comment_post_ID' => $p2, 'user_id' => 1, 'comment_approved' => '1' ) );
+		$c3 = $this->factory->comment->create( array( 'comment_post_ID' => $p3, 'user_id' => 1, 'comment_approved' => '1' ) );
+		
+		$comment_ids = get_comments( array(
+				'fields' => 'ids',
+				'post_author__in' => array( $author_id1 ),
+		) );
+		
+		$this->assertCount( 2, $comment_ids );
+	}
+	
+	/**
+	 * @ticket 29885
+	 */
+	function test_fields_post_author__not_in() {
+		$author_id1 = 111;
+		$author_id2 = 112;
+		
+		$p1 = $this->factory->post->create( array( 'post_author' => $author_id1	) );
+		$p2 = $this->factory->post->create( array( 'post_author' => $author_id1	) );
+		$p3 = $this->factory->post->create( array( 'post_author' => $author_id2	) );
+		
+		$c1 = $this->factory->comment->create( array( 'comment_post_ID' => $p1, 'user_id' => 1, 'comment_approved' => '1' ) );
+		$c2 = $this->factory->comment->create( array( 'comment_post_ID' => $p2, 'user_id' => 1, 'comment_approved' => '1' ) );
+		$c3 = $this->factory->comment->create( array( 'comment_post_ID' => $p3, 'user_id' => 1, 'comment_approved' => '1' ) );
+		
+		$comment_ids = get_comments( array(
+				'fields' => 'ids',
+				'post_author__not_in' => array( $author_id1 ),
+		) );
+		
+		$this->assertCount( 1, $comment_ids );
+	}
 }