The "test" vector api is implemented by vector "compare", please the following codes:
```
  @Override
    public abstract
    VectorMask<Byte> test(VectorOperators.Test op);

    /*package-private*/
    @ForceInline
    final
    <M extends VectorMask<Byte>>
    M testTemplate(Class<M> maskType, Test op) {
        ByteSpecies vsp = vspecies();
        if (opKind(op, VO_SPECIAL)) {
            ByteVector bits = this.viewAsIntegralLanes();
            VectorMask<Byte> m;
            if (op == IS_DEFAULT) {
                m = bits.compare(EQ, (byte) 0);
            } else if (op == IS_NEGATIVE) {
                m = bits.compare(LT, (byte) 0);
            }
            else {
                throw new AssertionError(op);
            }
            return maskType.cast(m);
        }
        int opc = opCode(op);
        throw new AssertionError(op);
    }
```
And the masked "test" is implemented by "&& test()" which could be optimized by using the masked vector "compare". This could save one "and" instruction for predicate feature supported architecture like ARM SVE and X86 AVX-512.