> > [Andy]
> >>How can you unit test nested functions?
[Raymond Hettinger]
> > For whitebox testing, you could make an inner function visible by
> > binding it to the enclosing function's attribute namespace.
> >
> > def f(x):
> > def g(y):
> > . . .
> > f.g = g # make g visible as an attribute of f
> > . . .
[Benji York]
> Note that when using this technique, f.g will not be bound until after
> you call the function:
That is a feature, not a bug. The inner function isn't even created
until the outer function is run.
>>> def f(x):
z = 30
def g(y):
return 10
return 20
>>> from dis import dis
>>> dis(f)
2 0 LOAD_CONST 1 (30)
3 STORE_FAST 1 (z)
3 6 LOAD_CONST 2 (<code object g at 00A33660,
file "<pyshell#37>", line 3>)
9 MAKE_FUNCTION 0
12 STORE_FAST 2 (g)
5 15 LOAD_CONST 3 (20)
18 RETURN_VALUE
The MAKE_FUNCTION step is where g comes into existence. That is a
run-time operation, not compile time.
If you are willing to be tricky, it is possible to write an accessor
function that goes into f.func_code.co_consts, finds the code object
whose co_name attribute is 'g', builds a wrapper function using
types.FunctionType, and returns the result for unittesting. But that
is not for the faint of heart ;-)
Raymond
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