RealSpan extends Span { @Override public TraceContext context() { return context; } RealSpan(TraceContext context,
    PendingSpans pendingSpans,
    MutableSpan state,
    Clock clock
  ); @Override boolean isNoop(); @Override TraceContext context(); @Override SpanCustomizer customizer(); @Override Span start(); @Override Span start(long timestamp); @Override Span name(String name); @Override Span kind(Kind kind); @Override Span annotate(String value); @Override Span annotate(long timestamp, String value); @Override Span tag(String key, String value); @Override Span error(Throwable throwable); @Override Span remoteServiceName(String remoteServiceName); @Override boolean remoteIpAndPort(String remoteIp, int remotePort); @Override void finish(); @Override void finish(long timestamp); @Override void abandon(); @Override void flush(); @Override String toString(); @Override boolean equals(Object o); @Override int hashCode();  }
@Test public void hasRealContext() { assertThat(span.context().spanId()).isNotZero(); }