testMultipleCommandsNotPermitted.java

@Suspendable
private String testMultipleCommandsNotPermitted(MemberInfo myInfo, MemberInfo otherMember, NotaryInfo notary) {
    try {
        IOUState iouState = new IOUState( //create sample output state for the test
                10,
                myInfo.getName(),
                otherMember.getName(),
                3,
                UUID.randomUUID(),
                Arrays.asList(myInfo.getLedgerKeys().get(0), otherMember.getLedgerKeys().get(0))
        );
        var txBuilder = ledgerService.createTransactionBuilder() //build sample transaction to test
                .setNotary(notary.getName())
                .setTimeWindowBetween(Instant.now(), Instant.now().plusMillis(Duration.ofDays(1).toMillis()))
                .addOutputState(iouState)
                .addInputState(inputStateRef)
                .addCommand(new IOUContract.Issue())
                .addCommand(new IOUContract.Transfer())
                .addSignatories(iouState.getParticipants());

        var signedTransaction = txBuilder.toSignedTransaction();//sign the test to check if it fails

        return "Fail";//no error found. Contract failed.


    } catch (Exception e) {//catching the error to see if the contract passed
        //check if gotten the expected error
        String exceptionMessage = e.getMessage() != null ? e.getMessage() : "No exception message";
        if (exceptionMessage.contains("Require a single command")) {
            return "Pass"; //expected error found so the contract passes the test
        } else {
            return "Contract failed but with a different Exception: " + e.getMessage();//different error thrown. Contract failed
        }
    }
}