The Jaguar TCS Racing driver set a 1m24.617s to go quickest of all on Friday at Circuit Ricardo Tormo - and half a second faster than the best time we saw at testing ahead of Season 9, the inaugural GEN3 campaign.
His late lap saw him pip longstanding timesheet-topping teammate Mitch Evans to the post, thrwarting his countryman's pitch to seal a clean sweep in Valencia, having set the pace in both of the prior sessions' running. Evans would end up third on the day.
Cassidy's time wasn't the best we'd seen this week, though, with Evans managing better in the opening session by a couple of tenths of a second.
Maximilian Guenther had been quickest in three of the last four tests in the Spanish city and the Maserati MSG Racing driver had set the pace last year. This time, he rounded out the third and final session in second spot between the Jaguars - 0.041 seconds back from Cassidy's pace.
Reigning champion Jake Dennis stuck the #1 Andretti into ninth spot come the chequered flag. Robin Frijns on his Envision Racing return finished fourth, Pascal Wehrlein in the TAG Heuer Porsche fifth and Norman Nato, on debut for Andretti this week, rounded out the top six.
Incredibly, all 21 runners on the day were split by just 0.7 seconds and a little over half a second separated the top 19 runners.
The morning started with a 27-lap race simulation giving teams and drivers the ability to test a full race program including ATTACK MODE activations, fast charging simulations, as well as caution and Safety Car periods.
Frijns led at the chequered flag having made it by Porsche's Antonio Felix da Costa in the final few laps. The session finished with Frijns P1, Evans P2 and da Costa in P3.
The official pre-season test marks the first and only time all 22 drivers and 11 teams are out on-track together before we head to Mexico City for the opening round of the 2023/24 ABB FIA Formula E World Championship on 13 January.