def test_Trace( self ):
"""
The correrct shortest destinations and distances are found
for start station 'A' in the exercise.
"""
t = Traversal( Route_Map( "Data/test_route_exercise.txt" ) )
t.traversals['A'] = {}
t.trace( 'A', 'A', 0 )
self.assertEqual( t.traversals, shortest_dests_from_A )
