hello3.php

<?php

  public function send(SendGrid\Email $email) {
    $form             = $email->toWebFormat();
    $form['api_user'] = $this->api_user; 
    $form['api_key']  = $this->api_key; 

    $response = $this->makeRequest($form);

    if ($response->code != 200) {
      throw new SendGrid\Exception($response->raw_body);
    }

    return $response->body;
  }

  public function makeRequest($form) {
    return \Unirest::post($this->url, array('User-Agent' => 'sendgrid/' . $this->version . ';php'), $form);
  }

hello4.php

<?php

/**
 * @expectedException SendGrid\Exception
 */
public function testSendGridExceptionThrownWhenNot200() {
  $mockResponse = (object)array("code" => 400, "raw_body" => '{"message": "error", "errors": ["Bad username / password"]}');

  $sendgrid = m::mock("SendGrid[makeRequest]", array("foo", "bar"));
  $sendgrid->shouldReceive('makeRequest')->once()->andReturn($mockResponse);

  $email = new SendGrid\Email();
  $email->setFrom("bar@foo.com")->
          setSubject("foobar subject")->
          setText("foobar text")->
          addTo("foo@bar.com");

  $response = $sendgrid->send($email);
}