send() public method

You'll probably want to use one of the convenience methods instead.
public send ( string $method, string $url, array $parameters = [], array $headers = [] ) : array
$method string The HTTP method to use.
$url string The URL to request.
$parameters array Optional. Query parameters.
$headers array Optional. HTTP headers.
return array Response data. - array|object body The response body. Type is controlled by Request::setReturnAssoc(). - array headers Response headers. - int status HTTP status code. - string url The requested URL.
 public function testSendReturnAssoc()
 {
     $request = new SpotifyWebAPI\Request();
     $request->setReturnAssoc(true);
     $response = $request->send('GET', 'https://api.spotify.com/v1/albums/7u6zL7kqpgLPISZYXNTgYk');
     $this->assertArrayHasKey('id', $response['body']);
 }
 public function testSendStatus()
 {
     $response = SpotifyWebAPI\Request::send('GET', 'https://api.spotify.com/v1/albums/7u6zL7kqpgLPISZYXNTgYk');
     $this->assertEquals(200, $response['status']);
 }