The pair remained team-mates after the tour with both players heading to France to join Racing Metro where they have been playing together in the Top 14.
On Saturday the pair will be on opposing sides when Ireland host Wales and Lydiate is relishing the chance to test himself against Sexton and the rest of the Irish Lions contingent.
"After the Lions tour there are a lot of Irish boys you are friendly with," he said.
"I am playing at Racing Metro now with (Ireland fly-half) Johnny Sexton, so I am really looking forward to coming up against him. I am sure there will be a few texts in the week.
"The last few games against Ireland have been real battles, and I expect it to be the same this time.
"The match will probably hinge on a couple of incidents that could swing either way, and it could be a good spectacle."