Handling test data that depends on temporal data (that might change while the test runs)

[Erik Jones]

On Thu, May 15, 2008 at 12:21 PM, Marcelo de Moraes Serpa <
celoserpa at gmail.com> wrote:

> Hello,
>
> So, I have this particular method, generate_chat_dir_string, which should
> generate a string in the following format:
>  "md5hexstring-day-month-year-hour-minute"
>
> This string will be used to create a directory in the filesystem.
>
> I'm trying to adopt the TDD approach, so, I'm starting by testing all the
> methods of the Chat class, including this one. However, an issue just popped
> up, this is the test code:
>
>
>    1.   def test_generate_chat_dir_string(self):
>    2.         import md5
>    3.         import random
>    4.         import datetime
>    5.         md5_handler = md5.new()
>    6.         users = [{"user":"pedro","atendente":False},{
>    "user":"joão","atendente":True}]
>    7.         #salt = random.random().to_s()
>    8.         #md5_handler.update(salt)
>    9.         now = datetime.datetime.now()
>    10.         ts = now.strftime("%d-%m-%Y-%H-%M")
>    11.         for user in users:
>    12.             md5_handler.update(user["user"])
>    13.
>    14.
>    15.         seed = md5_handler.hexdigest()
>    16.
>    17.         final_string = seed + "-" + ts
>    18.
>    19.         method_generated_string =
>    self.chat.generated_chat_dir_string(users,seed)
>    20.
>    21.         self.assertEquals(final_string,method_generated_string)
>
> As you can see, it generates a specific set of data and assembles a
> final_string. It then feeds the same data to generate_chat_dir_string and
> compare to see if the final_string is equal to the string generated by the
> tested method.
>
> However, they might not be equal becouse of the temporal data. In this case
> I'm not using seconds, but in a bizarre situation a minute could have passed
> and the test would faile becouse the two strings would have a different
> minute portion. Something like this:
>
> "b2ef9c7b10eb0985365f913420ccb84a-30-10-2008-10-31"
> "b2ef9c7b10eb0985365f913420ccb84a-30-10-2008-10-32"
>
> How could I handle this issue?
>
> Thanks in advance,


Add another parameter, with a default, to the method's interface:

def test_generate_chat_dir_string(self, now=None):
    if not now:
        import datetime
        now = datetime.datetime.now()
    .....


That way you can feed it values when testing to validate the calculations
but leave it up to the datetime module to fill in the used value in
production.



-- 
Erik Jones
mage2k at gmail.com
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