A pair of Clément Otazo penalties put France ahead in Grenoble before Paddy Jackson reduced the deficit with a kick and replacement Foster Horan scored a brilliant solo try that was converted by his captain.
Another two Otazo penalties restored the hosts' advantage before JJ Hanrahan scored with eight minutes remaining.
But there was a further twist in the tale when French No.8 Karl Chateau burrowed over in the last minute but the score was scrubbed off by the television match official.
That left Ruddock a relieved man and was quick to hail his side's monumental efforts in defence.
"It was a bit of a dogfight but we got a very important try from Foster. It was an excellent individual effort (from him) and we tackled and competed for the 50-50 possession very well," Ruddock told the Irish Examiner.
"In the end it was a sort of a scary moment when the referee and TMO came into it. France thought they scored a try at the death but it was shown not to be a try on the replay.
"There's always drama when an incident like that happens in the 79th minute and you wonder whether the decision is going to go your way or their way, but it was inconclusive."
"I thought it was fantastic defending by our lads (at the end) because we got lots of bodies around the ball carrier, got our hands under the ball and stopped what might have been a clear-cut try being scored.
"We have created some very good chances in both games to date, but haven't always nailed those and you need to do that in matches that are as close as they have been.
"There has been a lot of spirit and a lot of courage, though, and to win in France is no mean feat, so we'll take that in going forward."