### Question:
TraceMultiPropagator implements TextMapPropagator { public static Builder builder() { return new Builder(); } private  TraceMultiPropagator(List<TextMapPropagator> propagatorList); static Builder builder(); @Override List<String> fields(); @Override void inject(Context context, C carrier, Setter<C> setter); @Override Context extract(Context context, C carrier, Getter<C> getter);  }### Answer:
@Test void addPropagator_null() { assertThrows( NullPointerException.class, () -> TraceMultiPropagator.builder().addPropagator(null)); }