public function testMessageHeaderAccessors()
{
// A new message shouldn't have any RFC-822 headers set
$message = new SendGrid\Email();
$this->assertEquals('{}', $message->getMessageHeadersJson());
// Add some message headers, check they are correctly stored
$headers = array('X-Sent-Using' => 'SendGrid-API', 'X-Transport' => 'web');
$message->setMessageHeaders($headers);
$this->assertEquals($headers, $message->getMessageHeaders());
// Add another header, check if it is stored
$message->addMessageHeader('X-Another-Header', 'first_value');
$headers['X-Another-Header'] = 'first_value';
$this->assertEquals($headers, $message->getMessageHeaders());
// Replace a header
$message->addMessageHeader('X-Another-Header', 'second_value');
$headers['X-Another-Header'] = 'second_value';
$this->assertEquals($headers, $message->getMessageHeaders());
// Get the encoded headers; they must be a valid JSON
$json = $message->getMessageHeadersJson();
$decoded = json_decode($json, TRUE);
$this->assertInternalType('array', $decoded);
// Test we get the same message headers we put in the message
$this->assertEquals($headers, $decoded);
// Remove a header
$message->removeMessageHeader('X-Transport');
unset($headers['X-Transport']);
$this->assertEquals($headers, $message->getMessageHeaders());
}