public function testUseHeaders()
{
$email = new SendGrid\Email();
$email->addTo('*****@*****.**')->addBcc('*****@*****.**')->setFrom('*****@*****.**')->setSubject('Subject')->setHtml('Hello You');
$this->assertFalse($email->useHeaders());
$email->removeBcc('*****@*****.**');
$this->assertTrue($email->useHeaders());
$email->addCc('*****@*****.**');
$this->assertFalse($email->useHeaders());
$email->removeCc('*****@*****.**')->setRecipientsinHeader(true);
$this->assertTrue($email->useHeaders());
$email->setRecipientsinHeader(false);
$this->assertFalse($email->useHeaders());
$email->addBcc('*****@*****.**')->addAttachment('attachment.ext');
$this->assertTrue($email->useHeaders());
}