On Thu, Oct 1, 2015 at 5:46 PM, Ashwini Oruganti <ashfall@twistedmatrix.com> wrote:


On Thu, Oct 1, 2015 at 1:40 PM, Mashiat Sarker Shakkhar <mashiat.sarker@gmail.com> wrote:
Hi

I have a function that uses callLater extensively to schedule a number of different tasks. I don't want to get into the rationale behind such a design, but here is a contrived example which will help me explain my problem: 


    def b():

        '''Do some work'''


    def c():

        '''Do some more work'''


    def a(flag):

        if flag:

            return Reactor.callLater(300, b)

        else:

            return Reactor. callLater(100, c)


Now I want to test this function. Of course I can't wait for 5 minutes to ensure that `b` or `c` will indeed be called. What I need is some sort of mock clock which lets me fast forward time. Does any such thing exist in Twisted / Trial?




HI Ashwini

 Thanks a lot for your response. I did come across MemoryReactorClock before, but I could not figure out how to use it to test my code. I am using trial as the test runner, which allows me to pass the name of the reactor to be used in command line. But MemoryReactorClock is not available, because it is not in twisted.internet.

The code that I am testing imports reactor from twisted.internet in the global scope. Do I have to change that and pass a reactor explicitly (say, as a function parameter) where it is needed? Is there any other way to change the default reactor to MemoryReactorClock just for running tests?

Going with my previous example, do I have to rewrite the code like following or is there a better way?

    def b():

        '''Do some work'''


    def c():

        '''Do some more work'''


    def a(myreactor, flag):

        if flag:

            return myreactor.callLater(300, b)

        else:

            return myeactor. callLater(100, c)


I do see this in the documentation:

> New application code should prefer to pass and accept the reactor as a parameter where it is needed, rather than relying on being able to import this module to get a reference. This simplifies unit testing ...


But I'd prefer not to change the signature of existing functions.


Regards

Shakkhar