Tests rendering errors for nested fields.

Source

						public function testNestedFieldError() {
		$doc = new Document(array('data' => array('foo' => array('bar' => 'value'))));
		$doc->errors(array('foo.bar' => 'Something bad happened.'));

		$this->form->create($doc);
		$result = $this->form->field('foo.bar');

		$this->assertTags($result, array(
			array('div' => array()),
			'label' => array('for' => 'FooBar'), 'Foo Bar', '/label',
			'input' => array(
				'type' => 'text', 'name' => 'foo[bar]', 'id' => 'FooBar', 'value' => 'value'
			),
			'div' => array('class' => 'error'), 'Something bad happened.', '/div',
			array('/div' => array())
		));
	}