Nine different players scored tries as France beat Romania 62-14 in stifling heat in Bucharest on Saturday.
Castaignede won his 51st cap
Yannick Jauzion, Remy Martin, debutant Thierry Dusautoir and Damien Traille, who also kicked 20 points, all crossed as the visitors led 31-6 at half-time.
Sylvain Marconnet, Thomas Castaignede, Dimitri Szarzewski, Julien Laharrague and David Marty added further tries.
Romania did manage one try through winger Catalin Fercu but France move on to face South Africa in good heart.
The sides meet in Cape Town next Saturday, 24 June.
"The players took the match very seriously and really applied themselves," said France coach Bernard Laporte.
"I was pleased to see running rugby despite the heat. As for the new faces (David Attoub, Dusautoir and Vincent Debaty all made debuts), we saw some good things and less good things from each."
Captain Fabien Pelous added: "We had a hard time getting going and made a few mistakes early on but then we started to get on top. I think it was a job well done."
Castaignede was making his first start at fly-half for France in six years, with Frederic Michalak ruled out of the summer Tests with a shoulder injury.
France: Clement Poitrenaud; Philippe Bidabe, Yannick Jauzion, Damien Traille, Cedric Heymans; Thomas Castaignede, Pierre Mignoni; Sylvain Marconnet, Raphael Ibanez, David Attoub, Lionel Nallet, Fabien Pelous (capt), Thierry Dusautoir, Remy Martin, Julien Bonnaire.
Replacements: Dimitri Szarzewski, Vincent Debaty, Jerôme Thion, Imanol Harinordoquy, Dimitri Yachvili, David Marty, Julien Laharrague.
Romania: Florin Vlaicu; Catalin Fercu, Robert Dascalu, Romeo Gontineac, Ioan Teodorescu; Ionut Dimofte, Lucian Sirbu; Petru Balan, Marius Tincu, Bogdan Balan, Sorin Socol (captain), Cristi Petre, Stelian Burcea, Marian Tudori, Cosmin Ratiu.
Replacements: Cezar Popescu, Paulica Ion, Razvan Mavrodin, Valentin Ursache, Vali Calafeteanu, Gabriel Brezoianu, Iulian Dumitras.