@Test
public void testSpanAttributes() {

  OpencensusTracerFactory factory =
      new OpencensusTracerFactory(internalTracer, ImmutableMap.of("gax.version", "1.2.3"));
  factory.newTracer(
      NoopApiTracer.getInstance(), SpanName.of("FakeClient", "FakeMethod"), OperationType.Unary);
  verify(span, times(1))
      .putAttributes(
          ImmutableMap.of("gax.version", AttributeValue.stringAttributeValue("1.2.3")));
}