def test_tracer():
tracer = Tracer()
span = tracer.start_trace(operation_name='root')
child = tracer.join_trace(operation_name='child',
parent_trace_context=span.trace_context)
assert span == child
assert span.trace_context == child.trace_context
fut = tracer.close()
assert type(fut) is Future
fut.result(timeout=1)
