diff --git a/tests/phpunit/tests/walker.php b/tests/phpunit/tests/walker.php
new file mode 100644
index 0000000000..98b1658dd2
--- /dev/null
+++ b/tests/phpunit/tests/walker.php
@@ -0,0 +1,199 @@
+<?php
+
+/**
+ * @group post
+ * @group navmenus
+ * @group taxonomy
+ * @group walker
+ */
+class Tests_Walker extends WP_UnitTestCase {
+
+	function setUp() {
+
+		$this->walker = new Walker_Test();
+
+		parent::setUp();
+
+	}
+
+	function test_single_item() {
+
+		$items = array( (object) array( 'id' => 1, 'parent' => 0 ) );
+		$output = $this->walker->walk( $items, 0 );
+
+		$this->assertEquals( 1, $this->walker->get_number_of_root_elements( $items ) );
+		$this->assertEquals( '<li>1</li>', $output );
+
+	}
+
+	function test_single_item_flat() {
+
+		$items = array( (object) array( 'id' => 1, 'parent' => 0 ) );
+		$output = $this->walker->walk( $items, -1 );
+
+		$this->assertEquals( 1, $this->walker->get_number_of_root_elements( $items ) );
+		$this->assertEquals( '<li>1</li>', $output );
+
+	}
+
+	function test_single_item_depth_1() {
+
+		$items = array( (object) array( 'id' => 1, 'parent' => 0 ) );
+		$output = $this->walker->walk( $items, 1 );
+
+		$this->assertEquals( 1, $this->walker->get_number_of_root_elements( $items ) );
+		$this->assertEquals( '<li>1</li>', $output );
+
+	}
+
+	function test_multiple_items_single_level() {
+
+		$items = array( (object) array( 'id' => 1, 'parent' => 0 ), (object) array( 'id' => 2, 'parent' => 0 ) );
+
+		$output = $this->walker->walk( $items, 0 );
+
+		$this->assertEquals( 2, $this->walker->get_number_of_root_elements( $items ) );
+		$this->assertEquals( '<li>1</li><li>2</li>', $output );
+
+	}
+
+	function test_multiple_items_multiple_levels() {
+
+		$items = array( (object) array( 'id' => 1, 'parent' => 0 ), (object) array( 'id' => 2, 'parent' => 1 ) );
+
+		$output = $this->walker->walk( $items, 0 );
+
+		$this->assertEquals( 1, $this->walker->get_number_of_root_elements( $items ) );
+		$this->assertEquals( '<li>1<ul><li>2</li></ul></li>', $output );
+
+	}
+
+	function test_multiple_items_multiple_levels_flat() {
+
+		$items = array( (object) array( 'id' => 1, 'parent' => 0 ), (object) array( 'id' => 2, 'parent' => 1 ) );
+
+		$output = $this->walker->walk( $items, -1 );
+
+		$this->assertEquals( 1, $this->walker->get_number_of_root_elements( $items ) );
+		$this->assertEquals( '<li>1</li><li>2</li>', $output );
+
+	}
+
+	function test_multiple_items_multiple_levels_depth_1() {
+
+		$items = array( (object) array( 'id' => 1, 'parent' => 0 ), (object) array( 'id' => 2, 'parent' => 1 ) );
+
+		$output = $this->walker->walk( $items, 1 );
+
+		$this->assertEquals( 1, $this->walker->get_number_of_root_elements( $items ) );
+		$this->assertEquals( '<li>1</li>', $output );
+
+	}
+
+	function test_multiple_items_multiple_levels_depth_2() {
+
+		$items = array( (object) array( 'id' => 1, 'parent' => 0 ), (object) array( 'id' => 2, 'parent' => 1 ), (object) array( 'id' => 3, 'parent' => 2 ) );
+
+		$output = $this->walker->walk( $items, 2 );
+
+		$this->assertEquals( 1, $this->walker->get_number_of_root_elements( $items ) );
+		$this->assertEquals( '<li>1<ul><li>2</li></ul></li>', $output );
+
+	}
+
+	function test_multiple_items_recursive() {
+
+		$items = array( (object) array( 'id' => 1, 'parent' => 2 ), (object) array( 'id' => 2, 'parent' => 1 ) );
+
+		$output = $this->walker->walk( $items, 0 );
+
+		$this->assertEquals( 0, $this->walker->get_number_of_root_elements( $items ) );
+		$this->assertEquals( '<li>1<ul><li>2</li></ul></li>', $output );
+
+	}
+
+	function test_single_item_child() {
+
+		$items = array( (object) array( 'id' => 1, 'parent' => 3 ) );
+
+		$output = $this->walker->walk( $items, 0 );
+
+		$this->assertEquals( 0, $this->walker->get_number_of_root_elements( $items ) );
+		$this->assertEquals( '<li>1</li>', $output );
+
+	}
+
+	function test_single_item_missing_parent_depth_1() {
+
+		$items = array( (object) array( 'id' => 1, 'parent' => 3 ) );
+
+		$output = $this->walker->walk( $items, 1 );
+
+		$this->assertEquals( 0, $this->walker->get_number_of_root_elements( $items ) );
+
+		// It's not clear what the output of this "should" be
+
+		// Currently the item is simply returned
+		$this->assertEquals( '<li>1</li>', $output );
+
+		// But as we've only asked for the first depth maybe nothing should be returned?
+		//$this->assertEquals( '', $output );
+
+	}
+
+	function test_multiple_items_missing_parents() {
+
+		$items = array( (object) array( 'id' => 4, 'parent' => 1 ), (object) array( 'id' => 5, 'parent' => 2 ), (object) array( 'id' => 6, 'parent' => 3 ) );
+
+		$output = $this->walker->walk( $items, 0 );
+
+		$this->assertEquals( 0, $this->walker->get_number_of_root_elements( $items ) );
+		$this->assertEquals( '<li>4</li><li>5</li><li>6</li>', $output );
+
+	}
+
+	function test_multiple_items_missing_parents_depth_1() {
+
+		$items = array( (object) array( 'id' => 4, 'parent' => 1 ), (object) array( 'id' => 5, 'parent' => 2 ), (object) array( 'id' => 6, 'parent' => 3 ) );
+
+		$output = $this->walker->walk( $items, 1 );
+
+		$this->assertEquals( 0, $this->walker->get_number_of_root_elements( $items ) );
+
+		// It's not clear what the output of this "should" be
+
+		// Currently the first item is simply returned
+		$this->assertEquals( '<li>4</li>', $output );
+
+		// But as we've only asked for the first depth maybe nothing should be returned?
+		//$this->assertEquals( '', $output );
+
+		// Or maybe all items which are missing parents should simply be treat top level?
+		//$this->assertEquals( '<li>4</li><li>5</li><li>6</li>', $output );
+
+	}
+
+}
+
+class Walker_Test extends Walker {
+
+	var $tree_type = 'test';
+	var $db_fields = array ( 'parent' => 'parent', 'id' => 'id' );
+
+	function start_lvl( &$output, $depth = 0, $args = array() ) {
+		$output .= '<ul>';
+	}
+
+	function end_lvl( &$output, $depth = 0, $args = array() ) {
+		$output .= '</ul>';
+	}
+
+	function start_el( &$output, $item, $depth = 0, $args = array(), $current_page = 0 ) {
+		$output .= '<li>' . $item->id;
+	}
+
+	function end_el( &$output, $page, $depth = 0, $args = array() ) {
+		$output .= '</li>';
+	}
+
+}