The assertion "Throws: IllegalArgumentException — if op is not of Opcode.Kind.BRANCH" does not work as expected (see the attached test) for 72 instructions:
public static void main(String[] args) {
        Opcode[] opcodeList = Arrays.stream(Opcode.values()).
                filter(oc -> oc.kind() != Opcode.Kind.BRANCH).
                toArray(Opcode[]::new);
        for (int i = 0, j = 0; i < opcodeList.length; i++) {
            Opcode opcode = opcodeList[i];
            try {
                ClassFile.of().build(ClassDesc.of("Cls"), clsb -> {
                    clsb.withMethod("mtd", MethodTypeDesc.ofDescriptor("()I"),
                            ClassFile.ACC_STATIC,
                            mb -> mb.withCode(cb -> {
                                Label LBL = cb.newLabel();
                                cb.loadConstant(0);
                                cb.branch(opcode, LBL);
                                cb.loadConstant(1);
                                cb.ireturn();
                                cb.labelBinding(LBL);
                                cb.loadConstant(2);
                                cb.ireturn();
                            }));
                });
            } catch (IllegalArgumentException e) {
                continue;
            }
            System.out.println("%d) %s(%s) doesn't throw IllegalArgumentException as expected".
                    formatted(j++, opcode, opcode.kind()));
        }
    }