source: class B3PropagatorTest {
  
      @Test
      public void testExtractSampledOldFormat() {
  
target:         Map<String, String> headers = new HashMap<>();
  
          headers.put("X-B3-SpanId", "12345");
          headers.put("X-B3-TraceId", "67890");
          headers.put("X-B3-Sampled", "true"); // true/false instead of 0/1.
  
          B3Propagator subject = new B3Propagator();
  
          SpanContext span = subject.extract(new TextMapExtractAdapter(headers));
  
          // Although currently we do not use/propagate the (old) sampled value,
          // we want to make sure we always handle both the old and new formats.
          assertNotNull(span);
          assertEquals(span.toSpanId(), "12345");
          assertEquals(span.toTraceId(), "67890");
      }
  
  }