diff --git tests/phpunit/tests/export/class-wp-export-query.php tests/phpunit/tests/export/class-wp-export-query.php
new file mode 100644
index 0000000..0fd90d6
--- /dev/null
+++ tests/phpunit/tests/export/class-wp-export-query.php
@@ -0,0 +1,256 @@
+<?php
+
+/**
+ * Test WP_Export_Query class
+ *
+ * @group export
+ * @ticket 22435
+ */
+class Test_WP_Export_Query extends WP_UnitTestCase {
+	function setUp() {
+		if ( ! class_exists( 'WP_Export_Query' ) ) {
+			$this->markTestSkipped( "WP_Export_Query class doesn't exist" );
+		}
+
+		parent::setUp();
+	}
+
+	function test_WP_Export_Query_should_be_initialized_with_an_array() {
+		$export = new WP_Export_Query( array( 'author' => 'all' ) );
+		$this->assertTrue( (bool) $export );
+	}
+
+	function test_WP_Export_Query_should_use_post_ids_if_passed() {
+		$export = new WP_Export_Query( array( 'post_ids' => array( 1, 2, 3 ) ) );
+		$this->assertEquals( array( 1, 2, 3 ), $export->post_ids() );
+	}
+
+	function test_WP_Export_Query_should_filter_all_posts_if_all_arg_is_true() {
+		$post_id = $this->factory->post->create();
+		$export = new WP_Export_Query();
+		$this->assertEquals( array( $post_id ), $export->post_ids() );
+	}
+
+	function test_WP_Export_Query_should_filter_all_posts_if_no_args_passed() {
+		$post_id = $this->factory->post->create();
+		$export = new WP_Export_Query();
+		$this->assertEquals( array( $post_id ), $export->post_ids() );
+	}
+
+	function test_WP_Export_Query_should_not_export_anything_if_post_type_arg_is_set_to_non_existing_post_type() {
+		$post_id = $this->factory->post->create();
+		$export = new WP_Export_Query( array( 'post_type' => 'baba' ) );
+		$this->assertEquals( array(), $export->post_ids() );
+	}
+
+	function test_WP_Export_Query_should_filter_only_posts_with_a_certain_post_type_if_the_post_type_arg_is_set() {
+		register_post_type( 'baba' );
+		$post_id = $this->factory->post->create( array( 'post_type' => 'baba' ) );
+		$_       = $this->factory->post->create( array( 'post_type' => 'dyado' ) );
+		$export = new WP_Export_Query( array( 'post_type' => 'baba' ) );
+		$this->assertEquals( array( $post_id ), $export->post_ids() );
+		_unregister_post_type( 'baba' );
+	}
+
+	function test_WP_Export_Query_should_not_export_post_types_with_can_export_set_to_false() {
+		register_post_type( 'non-exportable', array( 'can_export' => false ) );
+		register_post_type( 'exportable', array( 'can_export' => true ) );
+		$non_exportable_post_id = $this->factory->post->create( array( 'post_type' => 'non-exportable' ) );
+		$exportable_post_id = $this->factory->post->create( array( 'post_type' => 'exportable' ) );
+		$export = new WP_Export_Query();
+		$this->assertEquals( array( $exportable_post_id ), $export->post_ids() );
+		_unregister_post_type( 'non-exportable' );
+		_unregister_post_type( 'exportable' );
+	}
+
+	function test_WP_Export_Query_should_not_export_auto_drafts_by_default() {
+		$post_id = $this->factory->post->create( array( 'post_status' => 'auto-draft' ) );
+		$export = new WP_Export_Query();
+		$this->assertEquals( array(), $export->post_ids() );
+	}
+
+	function test_WP_Export_Query_should_filter_only_posts_with_certain_status_if_status_arg_is_set() {
+		$post_id_baba = $this->factory->post->create( array( 'post_status' => 'baba' ) );
+		$post_id_dudu = $this->factory->post->create( array( 'post_status' => 'dudu' ) );
+		$export = new WP_Export_Query( array( 'status' => 'baba' ) );
+		$this->assertEquals( array( $post_id_baba ), $export->post_ids() );
+	}
+
+	function test_WP_Export_Query_should_filter_only_posts_with_certain_author_id_if_status_arg_is_a_number() {
+		$user_id = $this->factory->user->create();
+		$post_by_user = $this->factory->post->create( array( 'post_author' => $user_id ) );
+		$other_post = $this->factory->post->create( array( 'post_author' => $user_id + 1 ) );
+		$export = new WP_Export_Query( array( 'author' => $user_id ) );
+		$this->assertEquals( array( $post_by_user ), $export->post_ids() );
+	}
+
+	function test_WP_Export_Query_should_filter_only_posts_with_certain_author_name_if_status_arg_is_a_username() {
+		$user = $this->factory->user->create_and_get( array( 'user_login' => 'baba' ) );
+		$post_by_user = $this->factory->post->create( array( 'post_author' => $user->ID ) );
+		$other_post = $this->factory->post->create( array( 'post_author' => $user->ID + 1 ) );
+		$export = new WP_Export_Query( array( 'author' => 'baba' ) );
+		$this->assertEquals( array( $post_by_user ), $export->post_ids() );
+	}
+
+	function test_WP_Export_Query_should_filter_only_posts_with_certain_author_object_if_author_is_an_object_with_ID_member_variable() {
+		$user = $this->factory->user->create_and_get();
+		$post_by_user = $this->factory->post->create( array( 'post_author' => $user->ID ) );
+		$other_post = $this->factory->post->create( array( 'post_author' => $user->ID + 1 ) );
+		$export = new WP_Export_Query( array( 'author' => $user ) );
+		$this->assertEquals( array( $post_by_user ), $export->post_ids() );
+	}
+
+	function test_WP_Export_Query_should_filter_only_posts_after_certain_start_date_if_start_date_arg_is_passed() {
+		$post_before = $this->factory->post->create( array( 'post_date' => '2012-11-10 23:59:59' ) );
+		$post_after = $this->factory->post->create( array( 'post_date' => '2012-11-11 00:00:00' ) );
+		$export = new WP_Export_Query( array( 'start_date' => '2012-11-11' ) );
+		$this->assertEquals( array( $post_after ), $export->post_ids() );
+	}
+
+	function test_WP_Export_Query_should_filter_only_posts_after_certain_end_date_if_end_date_arg_is_passed() {
+		$post_before = $this->factory->post->create( array( 'post_date' => '2012-11-10 23:59:59' ) );
+		$post_after = $this->factory->post->create( array( 'post_date' => '2012-11-11 00:00:00' ) );
+		$export = new WP_Export_Query( array( 'end_date' => '2012-11-10' ) );
+		$this->assertEquals( array( $post_before ), $export->post_ids() );
+	}
+
+	function test_WP_Export_Query_should_filter_only_posts_with_certain_category_if_category_arg_is_passed() {
+		$category_id = $this->factory->category->create( array( 'name' => 'baba' ) );
+		$post_with_category = $this->factory->post->create( array( 'post_category' => array( $category_id ) ) );
+		$post_without = $this->factory->post->create();
+		$export = new WP_Export_Query( array( 'post_type' => 'post', 'category' => 'baba' ) );
+		$this->assertEquals( array( $post_with_category ), $export->post_ids() );
+	}
+
+	function test_WP_Export_Query_should_filter_only_posts_with_certain_category_id_if_category_arg_is_passed() {
+		$category_id = $this->factory->category->create( array( 'name' => 'baba' ) );
+		$post_with_category = $this->factory->post->create( array( 'post_category' => array( $category_id ) ) );
+		$post_without = $this->factory->post->create();
+		$export = new WP_Export_Query( array( 'post_type' => 'post', 'category' => $category_id ) );
+		$this->assertEquals( array( $post_with_category ), $export->post_ids() );
+	}
+
+	function test_WP_Export_Query_should_filter_posts_by_category_only_for_post_post_type() {
+		$category_id = $this->factory->category->create( array( 'name' => 'baba' ) );
+		$post_with_category = $this->factory->post->create( array( 'post_category' => array( $category_id ) ) );
+		$post_without = $this->factory->post->create();
+		$different_post_type = $this->factory->post->create( array( 'post_type' => 'page' ) );
+		$export = new WP_Export_Query( array( 'category' => $category_id ) );
+		$this->assertEqualSets( array( $post_with_category, $post_without, $different_post_type ), $export->post_ids() );
+	}
+
+	function test_WP_Export_Query_should_include_attachments_of_posts_if_we_are_filtering_only_some_post_types() {
+		register_post_type( 'baba' );
+		$post_id = $this->factory->post->create( array( 'post_type' => 'baba' ) );
+		$attachment_post_id = $this->factory->post->create( array( 'post_type' => 'attachment', 'post_parent' => $post_id ) );
+		$export = new WP_Export_Query( array( 'post_type' => 'baba' ) );
+		$this->assertEquals( array( $post_id, $attachment_post_id ), $export->post_ids() );
+		_unregister_post_type( 'baba' );
+	}
+
+	function test_authors_should_return_list_of_users_for_each_post_author() {
+		$user_id = $this->factory->user->create();
+		$this->factory->post->create( array( 'post_author' => $user_id ) );
+		$export = new WP_Export_Query();
+		$authors = $export->authors();
+		$this->assertEquals( 1, count( $authors ) );
+		$this->assertEquals( $user_id, $authors[0]->ID );
+	}
+
+	function test_authors_should_skip_non_existing_authors() {
+		$this->factory->post->create( array( 'post_author' => 11 ) );
+		$export = new WP_Export_Query();
+		$this->assertEquals( array(), $export->authors() );
+	}
+
+	function test_authors_should_skip_auto_draft_authors() {
+		$user_id = $this->factory->user->create();
+		$this->factory->post->create( array( 'post_author' => $user_id, 'post_status' => 'auto-draft' ) );
+		$export = new WP_Export_Query();
+		$this->assertEquals( array(), $export->authors() );
+	}
+
+	function test_categories_should_return_only_the_category_we_are_filtering_on() {
+		$category_id = $this->factory->category->create( array( 'name' => 'baba' ) );
+		$other_category_id = $this->factory->category->create( array( 'name' => 'dyado' ) );
+		$export = new WP_Export_Query( array( 'post_type' => 'post', 'category' => $category_id ) );
+		$this->assertEquals( 1, count( $export->categories() ) );
+	}
+
+	function test_categories_should_return_no_categories_if_we_are_requesting_only_one_post_type() {
+		$category_id = $this->factory->category->create();
+		$export = new WP_Export_Query( array( 'post_type' => 'post' ) );
+		$this->assertEquals( array(), $export->categories() );
+	}
+
+	function test_categories_should_return_all_categories_if_we_are_requesting_all_post_types() {
+		$category_id = $this->factory->category->create();
+		$another_category_id = $this->factory->category->create();
+		$export = new WP_Export_Query();
+		$this->assertEqualSets( array( 1, $category_id, $another_category_id ), self::get_term_ids( $export->categories() ) );
+	}
+
+	function test_categories_should_not_return_a_child_before_its_parent_category() {
+		$child_category_id = $this->factory->category->create();
+		$top_category_id = $this->factory->category->create();
+		wp_update_term( $child_category_id, 'category', array( 'parent' => $top_category_id ) );
+		$export = new WP_Export_Query();
+		$this->assertNoChildBeforeParent( $export->categories() );
+	}
+
+	function test_tags_should_return_all_tags() {
+		$tag_id = $this->factory->tag->create();
+		$export = new WP_Export_Query();
+		$this->assertEquals( array( $tag_id ), self::get_term_ids( $export->tags() ) );
+	}
+
+	function test_tags_should_return_no_tags_if_we_are_requesting_only_one_post_type() {
+		$category_id = $this->factory->tag->create();
+		$export = new WP_Export_Query( array( 'post_type' => 'post' ) );
+		$this->assertEquals( array(), $export->tags() );
+	}
+
+	function test_custom_taxonomies_terms_should_return_all_terms() {
+		register_taxonomy( 'taxonomy_all', 'post' );
+		$term_id = $this->factory->term->create( array( 'taxonomy' => 'taxonomy_all' ) );
+		$export = new WP_Export_Query();
+		$this->assertEquals( array( $term_id ), self::get_term_ids( $export->custom_taxonomies_terms() ) );
+		_unregister_taxonomy( 'taxonomy_all' );
+	}
+
+	function test_custom_taxonomes_terms_should_return_no_terms_if_we_are_requesting_only_one_post_type() {
+		register_taxonomy( 'taxonomy_one_post_type', 'post' );
+		$term_id = $this->factory->term->create( array( 'taxonomy' => 'taxonomy_one_post_type' ) );
+		$export = new WP_Export_Query( array( 'post_type' => 'post' ) );
+		$this->assertEquals( array(), $export->custom_taxonomies_terms() );
+		_unregister_taxonomy( 'taxonomy_one_post_type' );
+	}
+
+	function test_custom_taxonomies_terms_should_not_return_a_child_before_its_parent_term() {
+		register_taxonomy( 'heir', 'post', array( 'hierarchical' => true ) );
+		$child_term_id = $this->factory->term->create( array( 'taxonomy' => 'heir' ) );
+		$top_term_id = $this->factory->term->create( array( 'taxonomy' => 'heir' ) );
+		wp_update_term( $child_term_id, 'heir', array( 'parent' => $top_term_id ) );
+		$export = new WP_Export_Query();
+		$this->assertNoChildBeforeParent( $export->custom_taxonomies_terms() );
+		_unregister_taxonomy( 'heir' );
+	}
+
+	private function assertNoChildBeforeParent( $terms ) {
+		$visited = array();
+		foreach( $terms as $term ) {
+			$this->assertTrue( isset( $visited[$term->parent] ) || !$term->parent );
+			$visited[$term->term_id] = true;
+		}
+	}
+
+	private static function get_term_ids( $terms ) {
+		return array_values( array_map( array( __CLASS__, '_get_term_ids_cb' ), $terms ) );
+	}
+
+	private static function _get_term_ids_cb( $c ) {
+		return intval( $c->term_id );
+	}
+
+}
+
diff --git tests/phpunit/tests/export/functions.export.php tests/phpunit/tests/export/functions.export.php
new file mode 100644
index 0000000..e3b77e7
--- /dev/null
+++ tests/phpunit/tests/export/functions.export.php
@@ -0,0 +1,43 @@
+<?php
+
+/**
+ * Test export functions
+ *
+ * @group export
+ * @ticket 22435
+ */
+class Test_WP_Export_Functions extends WP_UnitTestCase {
+	function setUp() {
+		if ( ! function_exists( 'wp_export' ) ) {
+			$this->markTestSkipped( "wp_export function doesn't exist" );
+		}
+
+		parent::setUp();
+	}
+	
+	function test_wp_export_returns_wp_error_if_the_writer_throws_Export_exception() {
+		$this->assertTrue( is_wp_error( wp_export( array( 'writer' => 'Test_WP_Export_Stub_Writer_Throws_Export_Exception' ) ) ) );
+	}
+
+	function test_wp_export_passes_the_exception_if_the_writer_throws_other_exception() {
+		$this->setExpectedException( 'Exception' );
+		wp_export( array( 'writer' => 'Test_WP_Export_Stub_Writer_Throws_Other_Exception' ) );
+	}
+
+}
+
+class Test_WP_Export_Stub_Writer_Throws_Export_Exception {
+	function __construct( $formatter ) {
+	}
+	function export() {
+		throw new WP_Export_Exception( 'baba' );
+	}
+}
+
+class Test_WP_Export_Stub_Writer_Throws_Other_Exception {
+	function __construct( $formatter ) {
+	}
+	function export() {
+		throw new Exception( 'baba' );
+	}
+}
diff --git tests/phpunit/tests/export/writers.php tests/phpunit/tests/export/writers.php
new file mode 100644
index 0000000..6715d17
--- /dev/null
+++ tests/phpunit/tests/export/writers.php
@@ -0,0 +1,28 @@
+<?php
+
+/**
+ * Test WP_Export_*_Writer classes
+ *
+ * @group export
+ * @ticket 22435
+ */
+class Test_WP_Export_Writers extends WP_UnitTestCase {
+	function test_export_returner_returns_all_the_return_values() {
+		if ( ! class_exists( 'WP_Export_Returner' ) ) {
+			$this->markTestSkipped( "WP_Export_Returner class doesn't exist" );
+		}
+		$returner = new WP_Export_Returner( $this->get_x_formatter() );
+		$this->assertEquals( 'xxx' , $returner->export() );
+	}
+
+	private function get_x_formatter() {
+		$methods = array( 'before_posts', 'posts', 'after_posts' );
+		$formatter = $this->getMock( 'WP_Export_WXR_Formatter', $methods, array( null ) );
+		foreach( $methods as $method ) {
+			$return = 'posts' == $method? array( 'x' ) : 'x';
+			$formatter->expects( $this->once() )->method( $method )->with()->will( $this->returnValue( $return ) );
+		}
+		return $formatter;
+	}
+}
+
diff --git tests/phpunit/tests/iterators.php tests/phpunit/tests/iterators.php
new file mode 100644
index 0000000..bd5f0d7
--- /dev/null
+++ tests/phpunit/tests/iterators.php
@@ -0,0 +1,53 @@
+<?php
+
+/**
+ * @ticket 22435
+ */
+class Test_WP_Post_IDs_Iterator extends WP_UnitTestCase {
+	function setUp() {
+		if ( ! class_exists( 'WP_Post_IDs_Iterator' ) ) {
+			$this->markTestSkipped( "WP_Post_IDs_Iterator class doesn't exist" );
+		}
+
+		parent::setUp();
+	}
+
+	function test_create() {
+		new WP_Post_IDs_Iterator( array( 1, 2, 3 ) );
+	}
+
+	function test_no_posts() {
+		$this->assertIteratorReturnsSamePostIDs( array() );
+	}
+
+	function test_less_ids_than_limit() {
+		$post_id_0 = $this->factory->post->create();
+		$post_id_1 = $this->factory->post->create();
+		$this->assertIteratorReturnsSamePostIDs( array( $post_id_0, $post_id_1 ), 10 );
+	}
+
+	function test_ids_exactly_as_limit() {
+		$post_id_0 = $this->factory->post->create();
+		$post_id_1 = $this->factory->post->create();
+		$this->assertIteratorReturnsSamePostIDs( array( $post_id_0, $post_id_1 ), 2 );
+	}
+
+	function test_more_ids_than_limit() {
+		$post_id_0 = $this->factory->post->create();
+		$post_id_1 = $this->factory->post->create();
+		$post_id_2 = $this->factory->post->create();
+		$this->assertIteratorReturnsSamePostIDs( array( $post_id_0, $post_id_1, $post_id_2 ), 2 );
+	}
+
+	function test_ids_exactly_twice_more_than_limit() {
+		$post_id_0 = $this->factory->post->create();
+		$post_id_1 = $this->factory->post->create();
+		$post_id_2 = $this->factory->post->create();
+		$post_id_3 = $this->factory->post->create();
+		$this->assertIteratorReturnsSamePostIDs( array( $post_id_0, $post_id_1, $post_id_2, $post_id_3 ), 2 );
+	}
+
+	private function assertIteratorReturnsSamePostIDs( $post_ids, $limit = 2 ) {
+		$this->assertEquals( $post_ids, wp_list_pluck( iterator_to_array( new WP_Post_IDs_Iterator( $post_ids, $limit ) ), 'ID' ) );
+	}
+}