@Test
public void testExtract_mixedCaseIsLowered() {

    Map<String, String> mixedCaseHeaders = new HashMap<>();
    mixedCaseHeaders.put("X-B3-SpanId", Long.toHexString(1));
    mixedCaseHeaders.put("X-b3-traceId", Long.toHexString(2));
    mixedCaseHeaders.put("x-B3-sampled", "1");
    B3Propagator subject = new B3Propagator();
    SpanContext span = subject.extract(new TextMapExtractAdapter(mixedCaseHeaders));
    assertNotNull(span);
    assertEquals(span.getSpanId(), 1);
    assertEquals(span.getTraceId(), 2);
}