Add unit test to ensure that attachments are included

tests/phpunit/tests/export/attachments.php

@@ -0,0 +1,66 @@
+<?php
+
+/**
+ * @group export
+ * @group attachments
+ * @ticket 17379
+ */
+class Test_Export_Includes_Attachments extends WP_UnitTestCase {
+	protected static $post_1;
+	protected static $attachment_1;
+
+	public static function wpSetUpBeforeClass( WP_UnitTest_Factory $factory ) {
+		self::$post_1 = self::factory()->post->create_and_get(
+			array(
+				'post_title'  => 'Test Post 1',
+				'post_author' => $factory->user->create( array( 'role' => 'editor' ) ),
+			)
+		);
+
+		$post_2 = self::factory()->post->create_and_get(
+			array(
+				'post_title'  => 'Test Post 2',
+				'post_author' => $factory->user->create( array( 'role' => 'editor' ) ),
+			)
+		);
+
+		$file = DIR_TESTDATA . '/images/test-image.jpg';
+
+		self::$attachment_1 = $factory->attachment->create_upload_object( $file );
+
+		set_post_thumbnail( self::$post_1->ID, self::$attachment_1 );
+		set_post_thumbnail( $post_2, $factory->attachment->create_upload_object( $file ) );
+	}
+
+	/**
+	 * Tests the export function to ensure that attachments are included.
+	 *
+	 * Runs in a separate process to prevent "headers already sent" error.
+	 *
+	 * This test does not preserve global state to prevent the exception
+	 * "Serialization of 'Closure' is not allowed" when running in
+	 * a separate process.
+	 *
+	 * @runInSeparateProcess
+	 * @preserveGlobalState disabled
+	 */
+	public function test_export_includes_attachments_for_specific_author() {
+		require_once ABSPATH . 'wp-admin/includes/export.php';
+
+		ob_start();
+		export_wp(
+			array(
+				'content' => 'post',
+				'author'  => self::$post_1->post_author,
+			)
+		);
+		$xml = simplexml_load_string( ob_get_clean() );
+
+		$this->assertNotEmpty( $xml->channel->item->title );
+		$this->assertEquals( self::$post_1->ID, (int) $xml->channel->item[0]->children( 'wp', true )->post_id );
+		$this->assertEquals( self::$attachment_1, (int) $xml->channel->item[1]->children( 'wp', true )->post_id );
+
+		// Test that the post and attachment by the other author are not included by asserting that there are only two items.
+		$this->assertCount( 2, $xml->channel->item );
+	}
+}