Olivia Wilde has joked her romance with Jason Sudeikis has been one long 'Booksmart' audition.

The actress is making her feature film directorial debut on the movie in which Jason - with whom she has son Otis, five, and daughter Daisy, two - stars in as Principle Brown, and has teased that their eight year romance has been like one long audition for the role.

She said: ''His entire relationship with me has been one long audition for Booksmart and he nailed it.''

Despite her jokes, Olivia was blown away by Jason's performance, and says she ''loved'' being able to watch him work.

Speaking to 'Entertainment Tonight', she said: ''There's still a shorthand that comes from being someone's closest partner, but I loved being able to just set him free because he's one of the best improvisers in the world. And I just loved that we got him to take this bit of information that we had in the script and run with it.

''And he gave us so much. We were dying laughing behind the monitor the whole time. I was like, 'This is remarkable.' Not many people can do that, and I loved in the scenes with him, our girls, our two leads, Beanie and Kaitlyn, they're just looking at him like, 'How is he doing that?'''

Meanwhile, Olivia recently she was ''amazed'' by Jason's acting, although she says she was ''nervous'' about putting something ''personal'' on the screen.

She said: ''That was great. He's one of the best improvisers in the world so I knew I could cast him. He's like spinning a top and just letting it roll. It's really amazing to see him do his thing.

''I was nervous, for sure, because it's nerve-racking to take something totally personal and put it in front of the world, but I feel excited. The early response has been very positive. People are enjoying themselves and that's why we did it. I want to do it again. I love directing. I'm hooked.''