public void Tracer_ExtractAndInject_ShouldUseTheCorrectCodec()
{
var carrier = "carrier, yo";
var spanContext = Substitute.For <ILetsTraceSpanContext>();
_mockExtractor.Extract(Arg.Is <string>(c => c == carrier));
_mockInjector.Inject(Arg.Is <ISpanContext>(sc => sc == spanContext), Arg.Is <string>(c => c == carrier));
_builtTracer.Extract(_format, carrier);
_builtTracer.Inject(spanContext, _format, carrier);
_mockExtractor.Received(1).Extract(Arg.Any <string>());
_mockInjector.Received(1).Inject(Arg.Any <ISpanContext>(), Arg.Any <string>());
}