Tick the clock time by 300 milliseconds:
When I advance timers by 300 milliseconds
Tick the clock time by 1 millisecond:
When I advance timers by 1 millisecond
A preceding step "When I use fake timers" is required. For example:
When I use fake timers
And I advance timers by 300 milliseconds
When I advance timers by milliseconds:
Moves the clock the specified number of
milliseconds
. Any timers within the affected range of time will be called.