[Tutor] unwanted 'zero' ending

[Jim Mooney]

On 27 June 2013 05:38, Steven D'Aprano <steve at pearwood.info> wrote:

> Unit tests are great, but the learning curve is rather steep. I recommend that you start with doctests.

I tried a simple one and it worked, but a puzzlement. Does it Only
test what you've hard-coded? That is, here is a simple test:

def doubler(inp):
    '''Return a doubled number or string
    >>> doubler(24)
    48
    >>> doubler('zark')
    'zarkzark'
    '''
    return inp * 2

This works on 24 or 'zark' as input when I run
C:\Python33\Jimprogs>python -m doctest
"C:/python33/jimprogs/docstringtest.py" --verbose'
and doctest prints:
48
zarkzark

And it fails if I put 'this doesn't work' as the return value of the function:

1 items had failures:
   2 of   2 in docstringtest.
***Test Failed*** 2 failures.

Although that doesn't tell me much.

But it also works on different input --> 189 and 'plantagenet,' to print:
378
plantagenetplantagenet

It's odd to me that it doesn't fail on what I haven't hardcoded.

I don't see how docstring could figure what I might be doing, so I
assume that although it returns anything valid, it Only tests on the
hardcoded values, 24 and 'zark'.  Is this correct? In which case it
seems like a lot of hard coding would be needed unless you tested only
endpoints or what might be problematic.

Or is it doing something more?

-- 
Jim
Every  time I buy "As Seen on TV" it turns out to be junk.