Flush every cache of the site with the "Flush all caches" link of the home icon menu of the administration bar, and wait for the confirmation.
Examples
When I flush all caches from the administration bar
When we flush all caches from the administration bar
And I flush all caches from the administration bar
When I flush every cache from the administration bar
And we flush every cache from the administration bar
Pattern
When(/^(I |we )*flush (?:all caches|every cache) from the administration bar$/, …)
Part of @webship-js/backdrop-cms-steps (github.com/webship/backdrop-cms-steps), a step pack for Webship-js 2.0.x.