public function testGeneratesExtendedRequests()
{
$testConfig = $this->tokenRequestMinimal;
$o = new OAuth2($testConfig);
$o->setGrantType('urn:my_test_grant_type');
$o->setExtensionParams(['my_param' => 'my_value']);
// Generate the request and confirm that it's correct.
$req = $o->generateCredentialsRequest();
$this->assertInstanceOf('Psr\\Http\\Message\\RequestInterface', $req);
$this->assertEquals('POST', $req->getMethod());
$fields = Psr7\parse_query((string) $req->getBody());
$this->assertEquals('my_value', $fields['my_param']);
$this->assertEquals('urn:my_test_grant_type', $fields['grant_type']);
}