Mocking a variable in python

Question

I am trying to mock a variable that represents the a state of a device

In this case I have am trying to add a device and I have the following code:

if self.network.controller.add_node( secure ) :
    for i in range( 0, 60 ) :
        if flagStarted :
            if self.commandState == self.COMMAND_FAILED or self.commandState == self.COMMAND_FAILED :
            # Transaction Failed or Error
            self.network.controller.cancel_command( )
            self.log.warning( " *** Add Device Failed *** " )
            return False
        elif self.commandState == self.COMMAND_CANCEL :
            # Transaction Canceled
            self.log.debug( " *** Command Canceled " )
            return False
        elif self.commandState == self.COMMAND_COMPLETED :
            # Transaction Completed
            value = ZWaveProtocol.getAddedDevice( )
            if value > 0 :
                dev = DeviceCollection.getDeviceByProtocolID( value, "ZWave" )
                return dev.id
            else :
                if self.commandState == self.COMMAND_STARTING or self.commandState == self.COMMAND_WAITING :
                flagStarted = True
        sys.stdout.write( "." )
        sys.stdout.flush( )
        time.sleep( 1.0 )

    self.network.controller.cancel_command( )
    return -1
else :
    self.log.error( "Failed to add device" )

What am I am doing is mocking the self.network.controller.add_node( secure ) and when I do that I change the self.commandState to Starting.... What I wanted to accomplish is after about 5 seconds change it to self.COMMAND_COMPLETED in order to finish the operation successfully.

Any ideias how to mock this?

Answer 1

Since your code is blocking (programme flow stays on that loop until it is finished), an option without messing too much with your current code is to span a thread that changes the variable after a given time.

Let's assume that your code is inside a method called run_loop, and within a class MyClass. Given a simple test code like this:

def test_1():
  obj = MyClass()
  # Mock something
  obj.run_loop()
  # Do your assertions

You could change it to something like the following. I have not tested it, and can be refined a lot, but you get the idea:

from threading import Thread
from time import sleep

def change_state(obj):
    sleep(5)
    obj.commandState = obj.COMMAND_COMPLETE

def test_1():
  obj = MyClass()

  # Launch a thread that within 5 seconds will change the state of `obj`
  Thread(target=change_state, args=[obj]).start()

  # Call the main loop, which will recognize that the state changed within 5 secs
  obj.run_loop()