diff --git a/lib/ImportExport/OPML.php b/lib/ImportExport/OPML.php
index 032d753..6c650c8 100644
--- a/lib/ImportExport/OPML.php
+++ b/lib/ImportExport/OPML.php
@@ -44,20 +44,20 @@ class OPML {
                 $el->setAttribute("text", $r['name']);
                 $folders[$r['id']] = $el;
             }
-            // insert each folder into its parent node; for the root folder the parent is the document root node
-            foreach ($folders as $id => $el) {
-                $parent = $parents[$id] ?? $document->documentElement;
-                $parent->appendChild($el);
-            }
+        }
+        // insert each folder into its parent node; for the root folder the parent is the document root node
+        foreach ($folders as $id => $el) {
+            $parent = $folders[$parents[$id]] ?? $document->documentElement;
+            $parent->appendChild($el);
         }
         // create a DOM node for each subscription and insert them directly into their folder DOM node
         foreach (Arsse::$db->subscriptionList($user) as $r) {
             $el = $document->createElement(("outline"));
-            $el->setAttribute("text", $r['title']);
             $el->setAttribute("type", "rss");
+            $el->setAttribute("text", $r['title']);
             $el->setAttribute("xmlUrl", $r['url']);
             // include the category attribute only if there are tags
-            if (sizeof($tags[$r['id']])) {
+            if (isset($tags[$r['id']]) && sizeof($tags[$r['id']])) {
                 $el->setAttribute("category", implode(",", $tags[$r['id']]));
             }
             // if flat output was requested subscriptions are inserted into the root folder
diff --git a/tests/cases/ImportExport/TestOPML.php b/tests/cases/ImportExport/TestOPML.php
new file mode 100644
index 0000000..387400c
--- /dev/null
+++ b/tests/cases/ImportExport/TestOPML.php
@@ -0,0 +1,98 @@
+<?php
+/** @license MIT
+ * Copyright 2017 J. King, Dustin Wilson et al.
+ * See LICENSE and AUTHORS files for details */
+
+declare(strict_types=1);
+namespace JKingWeb\Arsse\TestCase\ImportExport;
+
+use JKingWeb\Arsse\Arsse;
+use JKingWeb\Arsse\Test\Result;
+use JKingWeb\Arsse\ImportExport\OPML;
+
+/** @covers \JKingWeb\Arsse\ImportExport\OPML<extended> */
+class TestOPML extends \JKingWeb\Arsse\Test\AbstractTest {
+    protected $folders = [
+        ['id' => 5, 'parent' => 3,    'children' => 0, 'feeds' => 1, 'name' => "Local"],
+        ['id' => 6, 'parent' => 3,    'children' => 0, 'feeds' => 2, 'name' => "National"],
+        ['id' => 4, 'parent' => null, 'children' => 0, 'feeds' => 0, 'name' => "Photography"],
+        ['id' => 3, 'parent' => null, 'children' => 2, 'feeds' => 0, 'name' => "Politics"],
+        ['id' => 2, 'parent' => 1,    'children' => 0, 'feeds' => 1, 'name' => "Rocketry"],
+        ['id' => 1, 'parent' => null, 'children' => 1, 'feeds' => 1, 'name' => "Science"],
+    ];
+    protected $subscriptions = [
+        ['id' => 3, 'folder' => 1,    'top_folder' => 1,    'unread' => 2,  'updated' => "2016-05-23 06:40:02", 'err_msg' => 'argh', 'title' => 'Ars Technica',   'url' => "http://example.com/3", 'favicon' => 'http://example.com/3.png'],
+        ['id' => 4, 'folder' => 6,    'top_folder' => 3,    'unread' => 6,  'updated' => "2017-10-09 15:58:34", 'err_msg' => '',     'title' => 'CBC News',       'url' => "http://example.com/4", 'favicon' => 'http://example.com/4.png'],
+        ['id' => 6, 'folder' => null, 'top_folder' => null, 'unread' => 0,  'updated' => "2010-02-12 20:08:47", 'err_msg' => '',     'title' => 'Eurogamer',      'url' => "http://example.com/6", 'favicon' => 'http://example.com/6.png'],
+        ['id' => 1, 'folder' => 2,    'top_folder' => 1,    'unread' => 5,  'updated' => "2017-09-15 22:54:16", 'err_msg' => '',     'title' => 'NASA JPL',       'url' => "http://example.com/1", 'favicon' => null],
+        ['id' => 5, 'folder' => 6,    'top_folder' => 3,    'unread' => 12, 'updated' => "2017-07-07 17:07:17", 'err_msg' => '',     'title' => 'Ottawa Citizen', 'url' => "http://example.com/5", 'favicon' => ''],
+        ['id' => 2, 'folder' => 5,    'top_folder' => 3,    'unread' => 10, 'updated' => "2011-11-11 11:11:11", 'err_msg' => 'oops', 'title' => 'Toronto Star',   'url' => "http://example.com/2", 'favicon' => 'http://example.com/2.png'],
+    ];
+    protected $tags = [
+        ['id' => 1, 'name' => "Canada", 'subscription' => 2],
+        ['id' => 1, 'name' => "Canada", 'subscription' => 4],
+        ['id' => 1, 'name' => "Canada", 'subscription' => 5],
+        ['id' => 2, 'name' => "Politics", 'subscription' => 4],
+        ['id' => 2, 'name' => "Politics", 'subscription' => 5],
+        ['id' => 3, 'name' => "Science, etc", 'subscription' => 1],
+        ['id' => 3, 'name' => "Science, etc", 'subscription' => 3],
+        // Eurogamer is untagged
+    ];
+    protected $serialization = <<<OPML_EXPORT_SERIALIZATION
+<?xml version="1.0" encoding="utf-8"?>
+<opml version="2.0">
+<head/>
+<body>
+    <outline text="Photography"/>
+    <outline text="Politics">
+        <outline text="Local">
+            <outline type="rss" text="Toronto Star" xmlUrl="http://example.com/2" category="Canada"/>
+        </outline>
+        <outline text="National">
+            <outline type="rss" text="CBC News" xmlUrl="http://example.com/4" category="Canada,Politics"/>
+            <outline type="rss" text="Ottawa Citizen" xmlUrl="http://example.com/5" category="Canada,Politics"/>
+        </outline>
+    </outline>
+    <outline text="Science">
+        <outline text="Rocketry">
+            <outline type="rss" text="NASA JPL" xmlUrl="http://example.com/1" category="Science etc"/>
+        </outline>
+        <outline type="rss" text="Ars Technica" xmlUrl="http://example.com/3" category="Science etc"/>
+    </outline>
+    <outline type="rss" text="Eurogamer" xmlUrl="http://example.com/6"/>
+</body>
+</opml>
+OPML_EXPORT_SERIALIZATION;
+    protected $serializationFlat = <<<OPML_EXPORT_SERIALIZATION
+<?xml version="1.0" encoding="utf-8"?>
+<opml version="2.0">
+<head/>
+<body>
+    <outline type="rss" text="Ars Technica" xmlUrl="http://example.com/3" category="Science etc"/>
+    <outline type="rss" text="CBC News" xmlUrl="http://example.com/4" category="Canada,Politics"/>
+    <outline type="rss" text="Eurogamer" xmlUrl="http://example.com/6"/>
+    <outline type="rss" text="NASA JPL" xmlUrl="http://example.com/1" category="Science etc"/>
+    <outline type="rss" text="Ottawa Citizen" xmlUrl="http://example.com/5" category="Canada,Politics"/>
+    <outline type="rss" text="Toronto Star" xmlUrl="http://example.com/2" category="Canada"/>
+</body>
+</opml>
+OPML_EXPORT_SERIALIZATION;
+
+    public function setUp() {
+        Arsse::$db = \Phake::mock(\JKingWeb\Arsse\Database::class);
+    }
+
+    public function testExportToOpml() {
+        \Phake::when(Arsse::$db)->folderList("john.doe@example.com")->thenReturn(new Result($this->folders));
+        \Phake::when(Arsse::$db)->subscriptionList("john.doe@example.com")->thenReturn(new Result($this->subscriptions));
+        \Phake::when(Arsse::$db)->tagSummarize("john.doe@example.com")->thenReturn(new Result($this->tags));
+        $this->assertXmlStringEqualsXmlString($this->serialization, (new OPML)->export("john.doe@example.com"));
+    }
+
+    public function testExportToFlatOpml() {
+        \Phake::when(Arsse::$db)->folderList("john.doe@example.com")->thenReturn(new Result($this->folders));
+        \Phake::when(Arsse::$db)->subscriptionList("john.doe@example.com")->thenReturn(new Result($this->subscriptions));
+        \Phake::when(Arsse::$db)->tagSummarize("john.doe@example.com")->thenReturn(new Result($this->tags));
+        $this->assertXmlStringEqualsXmlString($this->serializationFlat, (new OPML)->export("john.doe@example.com", true));
+    }
+}
diff --git a/tests/phpunit.xml b/tests/phpunit.xml
index 7c698ab..fd5429f 100644
--- a/tests/phpunit.xml
+++ b/tests/phpunit.xml
@@ -113,5 +113,8 @@
         <file>cases/Service/TestService.php</file>
         <file>cases/CLI/TestCLI.php</file>
     </testsuite>
+    <testsuite name="Import/Export">
+        <file>cases/ImportExport/TestOPML.php</file>
+    </testsuite>
 </testsuites>
 </phpunit>