public static L3ModificationInstruction modL3IPv6Src(IpAddress addr) {
        checkNotNull(addr, "Src l3 IPv6 address cannot be null");
        return new ModIPInstruction(L3SubType.IPV6_SRC, addr);
    }
@Test
    public void testModL3IPv6SrcMethod() {
        final Instruction instruction = Instructions.modL3IPv6Src(ip61);
        final L3ModificationInstruction.ModIPInstruction modIPInstruction =
                checkAndConvert(instruction,
                        Instruction.Type.L3MODIFICATION,
                        L3ModificationInstruction.ModIPInstruction.class);
        assertThat(modIPInstruction.ip(), is(equalTo(ip61)));
        assertThat(modIPInstruction.subtype(),
                is(equalTo(L3ModificationInstruction.L3SubType.IPV6_SRC)));
    }