Rasmussen is fresh off a banner season in the second-tier series previously known as Indy Lights, where the Dane claimed five wins, a further three podiums and sat on the pole five times en route to the title.
While there are aspirations to find a seat on the grid for next season, the 23-year-old remains tempered in his approach.
“For the time being, that's all it is, is a test,” Rasmussen said. “It's going to be me and Oliver Askew and we'll see what that leads to.”
His only previous test in IndyCar came with Andretti Global (then known as Andretti Autosport) in July 2022 at Mid-Ohio. With this opportunity coming at the end of the season instead of middle, there has been more time to put in the work to prepare.
Following the season finale at Laguna Seca, ECR equipped him with time in Chevrolet’s simulator in North Carolina, which Rasmussen said had been “something new for me”.
Additionally, there has been more time to also get familiar with the team, get fitted to the car and spend valuable time in the workshop.
“I love coming to Barber,” said Rasmussen, won from pole at the 2.3-mile Barber track in April to commence his successful championship push.
“It's going to be intense. That's a physical track, but I'll be up for the challenge and am looking forward to it.”
ECR ran 2012 champion Ryan Hunter-Reay alongside Rinus VeeKay for the final 10 races in 2023 after parting company with Conor Daly following Detroit.
Although locking up a ride for next year is the offseason priority that Rasmussen hopes to get resolved “as soon as possible,” the variables such as hybrid testing means he won’t panic until it’s time to go racing in St. Petersburg in March.
“There's so many moving parts in the IndyCar world right now, so I don't know what you can expect,” he said.
“I don't think you can really put a timeline on it. For me, obviously it would be nice to get it resolved soon.”
Rasmussen will share his seat in the test with 2019 Indy NXT champion Askew, who hasn’t competed in IndyCar since 2021.
The American lost his ride with McLaren at the end of a 2020 rookie season disrupted by missing two races due to a concussion suffered in the Indianapolis 500, before contesting a bit-part campaign in '21 filling in at three different teams. This included ECR, at Road America, after VeeKay was injured in a cycling crash.
He also subbed for his McLaren replacement Felix Rosenqvist in Detroit, and joined Rahal Letterman Lanigan Racing for the final three races to record a best finish of ninth at Laguna Seca.
Askew spent 2022 racing in Formula E for Andretti, peaking with fourth in London before losing his drive to Andre Lotterer.