	0	b : 0
	0	a : 1
	10	c : 0	[by a:=1]
glitch X on A 
WARNING: weak-interference `c'
>> cause: `a' (val: X)
	10	a : X
event queue:
	20	c : X	[from a:=X]
	13	b : 1
event queue:
	20	c : X	[from a:=X]
expect c -> 0 to overtake X 
	20	c : X	[by a:=X]
time: 20
assert failed: expecting node `c' at 0, but got X.
... at line 21
