@Test
public void testSetTag_numberTypeNullKey() {

    Span result = undertest.setTag((String)null, 1);
    assertSame(result, undertest);
    verify(abstractTracer).debug("key (null) or value (1) is null, ignoring");
    assertTrue("When key is null, should not be added to attributes", grpcSpan.getTagsList().isEmpty());
}