event queue:
check queue:
	time	eid	pid	event
	0	0	1	null
X : chan(int<32>) X = (0) [empty]
z : int z = 0
event queue:
check queue:
	time	eid	pid	event
	10	1	0	
X : chan(int<32>) X = (0) [empty]
z : int z = 0
event queue:
check queue:
	time	eid	pid	event
	20	2	0	X!(11)
	20	3	0	X?(z)
X : chan(int<32>) X = (0) [empty]
z : int z = 0
event queue:
	time	eid	pid	event
	20	2	0	X!(11)
check queue:
	30	4	0	
X : chan(int<32>) X = (11) [recvd]
z : int z = 11
expect only null join event in queue 
event queue:
check queue:
	time	eid	pid	event
	30	4	0	
	30	4	0	
X : chan(int<32>) X = (11) [empty]
z : int z = 11
expect empty queue 
event queue:
check queue:
	(empty)
X : chan(int<32>) X = (11) [empty]
z : int z = 11
time: 30
