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Asserts that the operation is causing a halt

I have a generator that I want to confirm has ended (at some point in the program. I am using unittest in python 2.7

# it is a generator whould have only one item
item = it.next()
# any further next() calls should raise StopIteration
self.assertRaises(StopIteration, it.next())

But it fails with the message

======================================================================
ERROR: test_productspider_parse_method (__main__.TestMyMethods)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/home/myName/tests/__main__.py", line 94, in test_my_method
    self.assertRaises(StopIteration, it.next())
StopIteration

----------------------------------------------------------------------
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1 answer


You need to pass the method itself instead of calling the method. In other words, drop the parentheses.

self.assertRaises(StopIteration, it.next)


Or you can use it as a context manager:

with self.assertRaises(StopIteration):
    it.next()
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