fkooman\OAuth\Client\Callback::handleCallback PHP Method

    public function handleCallback(array $query)
    {
        $queryState = isset($query['state']) ? $query['state'] : null;
        $queryCode = isset($query['code']) ? $query['code'] : null;
        $queryError = isset($query['error']) ? $query['error'] : null;
        $queryErrorDescription = isset($query['error_description']) ? $query['error_description'] : null;
        if (null === $queryState) {
            throw new CallbackException('state parameter missing');
        }
        $state = $this->tokenStorage->getState($this->clientConfigId, $queryState);
        if (false === $state) {
            throw new CallbackException('state not found');
        }
        // avoid race condition for state by really needing a confirmation
        // that it was deleted
        if (false === $this->tokenStorage->deleteState($state)) {
            throw new CallbackException('state already used');
        }
        if (null === $queryCode && null === $queryError) {
            throw new CallbackException('both code and error parameter missing');
        }
        if (null !== $queryError) {
            // FIXME: this should probably be CallbackException?
            throw new AuthorizeException($queryError, $queryErrorDescription);
        }
        if (null !== $queryCode) {
            $t = new TokenRequest($this->httpClient, $this->clientConfig);
            $tokenResponse = $t->withAuthorizationCode($queryCode);
            if (false === $tokenResponse) {
                throw new CallbackException('unable to fetch access token with authorization code');
            }
            if (null === $tokenResponse->getScope()) {
                // no scope in response, we assume we got the initially requested scope
                $scope = $state->getScope();
            } else {
                // the scope we got should be a superset of what we requested
                $scope = $tokenResponse->getScope();
                if (!$scope->hasScope($state->getScope())) {
                    // we didn't get the scope we requested, stop for now
                    // FIXME: we need to implement a way to request certain
                    // scope as being optional, while others need to be
                    // required
                    throw new CallbackException('requested scope not obtained');
                }
            }
            // store the access token
            $accessToken = new AccessToken(array('client_config_id' => $this->clientConfigId, 'user_id' => $state->getUserId(), 'scope' => $scope, 'access_token' => $tokenResponse->getAccessToken(), 'token_type' => $tokenResponse->getTokenType(), 'issue_time' => time(), 'expires_in' => $tokenResponse->getExpiresIn()));
            $this->tokenStorage->storeAccessToken($accessToken);
            // if we also got a refresh token in the response, store that as
            // well
            if (null !== $tokenResponse->getRefreshToken()) {
                $refreshToken = new RefreshToken(array('client_config_id' => $this->clientConfigId, 'user_id' => $state->getUserId(), 'scope' => $scope, 'refresh_token' => $tokenResponse->getRefreshToken(), 'issue_time' => time()));
                $this->tokenStorage->storeRefreshToken($refreshToken);
            }
            return $accessToken;
        }
    }

 public function testXYZ()
 {
     $client = new Client();
     $mock = new MockPlugin();
     $mock->addResponse(new Response(200, null, json_encode(array("access_token" => "my_access_token", "token_type" => "BeArEr", "refresh_token" => "why_not_a_refresh_token"))));
     $client->addSubscriber($mock);
     $state = new State(array("state" => "my_state", "client_config_id" => "foo", "issue_time" => time() - 100, "user_id" => "my_user_id", "scope" => Scope::fromString("foo bar")));
     $this->storage->storeState($state);
     $callback = new Callback("foo", $this->clientConfig[0], $this->storage, $client);
     $tokenResponse = $callback->handleCallback(array("state" => "my_state", "code" => "my_code"));
     $this->assertEquals("my_access_token", $tokenResponse->getAccessToken());
 }