fails:Fiber#kill kills a non-resumed fiber
fails:Fiber#kill kills a resumed fiber
fails:Fiber#kill executes the ensure block
fails:Fiber#kill repeatedly kills a fiber
fails:Fiber#kill propagates an exception raised by the ensure block to the killing fiber
fails:Fiber#kill kills a fiber which transferred, from the fiber it transferred to
fails:Fiber#kill kills a fiber whose ensure block transfers to another fiber
fails:Fiber#kill does nothing when killing a fiber twice
fails:Fiber#kill runs the ensure block in the fiber being killed, while it is still alive
