text: ##########################################################################
  #
  #  Copyright (c) 2018, Image Engine Design Inc. All rights reserved.
  #
  #  Redistribution and use in source and binary forms, with or without
  #  modification, are permitted provided that the following conditions are
  #  met:
  #
  #      * Redistributions of source code must retain the above
  #        copyright notice, this list of conditions and the following
  #        disclaimer.
  #
  #      * Redistributions in binary form must reproduce the above
  #        copyright notice, this list of conditions and the following
  #        disclaimer in the documentation and/or other materials provided with
  #        the distribution.
  #
  #      * Neither the name of John Haddon nor the names of
  #        any other contributors to this software may be used to endorse or
  #        promote products derived from this software without specific prior
  #        written permission.
  #
  #  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
  #  IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
  #  THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  #  PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
  #  CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
  #  EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
  #  PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
  #  PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
  #  LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
  #  NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
  #  SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  #
  ##########################################################################
  
  import unittest
  
  import IECore
  
  class CancellerTest( unittest.TestCase ) :
  
  	def testCheck( self ) :
  
  		IECore.Canceller.check( None )
  
  		c = IECore.Canceller()
  		IECore.Canceller.check( c )
  		c.cancel()
  
  		with self.assertRaises( IECore.Cancelled ) :
  			IECore.Canceller.check( c )
  
  	def testFinally( self ) :
  
  		def f() :
  
  			c = IECore.Canceller()
  			c.cancel()
  
  			didFinally = False
  			try :
  				IECore.Canceller.check( c )
  			finally :
  				didFinally = True
  
  			self.assertEqual( didFinally, True )
  
  		self.assertRaises( IECore.Cancelled, f )
  
  	def testCancelledClass( self ) :
  
  		self.assertIsInstance( IECore.Cancelled(), RuntimeError )
  		self.assertEqual( IECore.Cancelled.__module__, "IECore" )
  
  	def testExceptionTranslation( self ) :
  
  		def raiser( key ) :
  
  			raise IECore.Cancelled()
  
  		c = IECore.LRUCache( raiser, 1 )
  
  		with self.assertRaises( IECore.Cancelled ) as a :
  
  			# Expected sequence of events is as follows :
  			#
  			# 1. `get()` enters C++.
  			# 2. C++ enters back into Python, calling `raiser()`.
  			# 3. `raiser()` raises a _python_ exception containing a _python_
  			#    `IECore.Cancelled` object.
  			# 4. `LRUCacheGetter` (in LRUCacheBinding.cpp) calls `translatePythonException()` to turn the
  			#    Python exception back into an appropriate C++ one - a true instance of `IECore::Cancelled`.
  			# 5. The C++ exception propagates back to `get()`, which translates it back into Python,
  			#    yielding us an instance of `IECore.Cancelled`.
  			#
  			# If 4 or 5 fail to perform the appropriate translation, we'll end up with a generic
  			# exception being thrown, meaning we can no longer determine that cancellation occurred.
  			# And then bad things happen.
  
  			c.get( "test" )
  
  if __name__ == "__main__":
  	unittest.main()
  