def test_join_trace():
tracer = Tracer()
span = tracer.join(operation_name='test',
format=Format.TEXT_MAP, carrier={})
span.set_tag('x', 'y')
span.log_event('z')
child = tracer.start_span('child', parent=span)
child.log_event('w')
child.finish()
span.finish()
