public function test_draw_rectangle()
{
$c = new canvas(20, 4);
//draw a point
$this->assertTrue($c->draw_rectangle(array(1, 1), array(1, 1)));
//draw a line
$this->assertTrue($c->draw_rectangle(array(1, 2), array(6, 2)));
//draw a rectangle
$this->assertTrue($c->draw_rectangle(array(16, 1), array(20, 3)));
}