public function testRpos()
{
$this->assertNull(StringHelper::rpos(null, 'sad'));
$this->assertNull(StringHelper::rpos('a', 'sad', 10));
$this->assertEquals(1, StringHelper::rpos('lakanahbaha', 'a', -1));
$this->assertEquals(10, StringHelper::rpos('lakanahbahakjlapaosa', 'a', -5));
$this->assertEquals(19, StringHelper::rpos('lakanahbahakjlapaosa', 'a', 1));
$this->assertEquals(16, StringHelper::rpos('lakanahbahakjlapaosa', 'a', 2));
}
