扭曲延迟测试

Question

I have been struggling to wrap my head around testing twisted code with deferred's and deferred's in general.

I have a simple test that really should fail, I think.

From my undertstanding in Twisted's test tool Trial, I should be able to return a deferred and when it is finished the test will finish.

Here is my tidbit of code, maybe someone can help.

import unittest, time

from twisted.internet import reactor, defer

class MyTest(unittest.TestCase):

def test_simple_deferred(self):

    print "\nStarting Test"

    my_deferred = defer.Deferred()

    def print_time():
      print time.time()
      self.assertTrue(False)

    my_deferred.addCallback(print_time)

    reactor.callLater(3, my_deferred.callback)

    print time.time()

    return my_deferred

Thanks in advance, I have looked at a lot of examples, but I think I have gotten to the point that I have been looking at this for far too long.

Answer 1

You have two problems.

Firstly, to get the special deferred handling, your test case needs to inherit from twisted.trial.unittest.TestCase , not the python standard library version.

Lastly, you are not calling reactor.callLater properly, or rather, you aren't giving it the right arguments for Deferred.callback() ; you need to give the deferred a value . If you don't care what it is, give it a None . Likewise, the callback needs to take that argument; you can safely ignore it.

from twisted.trial import unittest
#^^^^^^^^^^^^^^^^^
import time

from twisted.internet import defer
from twisted.internet import reactor

class MyTest(unittest.TestCase):

    def test_simple_deferred(self):

        print "\nStarting Test"

        my_deferred = defer.Deferred()

        def print_time(dont_care):
        #              ^^^^^^^^^
            print time.time()
            self.assertTrue(False)

        my_deferred.addCallback(print_time)

        reactor.callLater(3, my_deferred.callback, None)
        #                                        ^^^^^^    
        print time.time()

        return my_deferred