GlobalTracer implements Tracer { public static Tracer get() { return INSTANCE; } private  GlobalTracer(); static Tracer get(); static boolean isRegistered(); static synchronized boolean registerIfAbsent(final Callable<Tracer> provider); static synchronized boolean registerIfAbsent(final Tracer tracer); @Deprecated static void register(final Tracer tracer); @Override ScopeManager scopeManager(); @Override SpanBuilder buildSpan(String operationName); @Override void inject(SpanContext spanContext, Format<C> format, C carrier); @Override SpanContext extract(Format<C> format, C carrier); @Override Span activeSpan(); @Override Scope activateSpan(Span span); @Override void close(); @Override String toString();  }
@Test public void testGet_SingletonReference() { Tracer tracer = GlobalTracer.get(); assertThat(tracer, is(instanceOf(GlobalTracer.class))); assertThat(tracer, is(sameInstance(GlobalTracer.get()))); }