public function testGeneratesAssertionRequests()
{
$testConfig = $this->tokenRequestMinimal;
$o = new OAuth2($testConfig);
$o->setSigningKey('a_key');
$o->setSigningAlgorithm('HS256');
// 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(OAuth2::JWT_URN, $fields['grant_type']);
$this->assertTrue(array_key_exists('assertion', $fields));
}