Juergen Klopp believes Borussia Dortmund passed an important test on Saturday, coming from behind to beat Mainz 2-1 in the Bundesliga.
Klopp's former side took an early lead through Marco Caligiuri, but goals from Marco Reus and Robert Lewandowski ensured the visitors made it four straight wins in all competitions.
Klopp said he enjoyed being involved in such a testing encounter, and was ultimately relieved to have bagged all three points.
"This was an incredibly intense game," Klopp said.
"Caligiuri's heroics were impressive, but we were then extremely clinical.
"We made a really good football match out of it. This was a test of our mettle and we passed it."
Dortmund's win has left the reigning Bundesliga champions second in the table after 13 matches, but still nine points behind runaway leaders Bayern Munich, who have only dropped five points in the league so far this season.