public Span toSpan(TraceContext context) {
    return toSpan(null, context);
  }
@Test void toSpan_decorates_unsampled() {
    propagationFactory = baggageFactory;
    TraceContext incoming = TraceContext.newBuilder().traceId(1L).spanId(2L).sampled(false).build();

    TraceContext toSpan = tracer.toSpan(incoming).context();
    assertThat(toSpan).isNotSameAs(incoming);
    assertThat(toSpan.extra()).isNotEmpty();
  }