Supposing that you have to write a solidity unit test and you expect the result as an error message, you can use the following pattern, simply using catch in the unit testing instead of or beside then:
contract('Contract', function(accounts) {
it("test Contract from wrong account", function() {
return Contract.deployed().then(function(instance) {
return Contract.callFunction(<params>);
}).then(function(balance) {
assert(false, "Call should not be allowed");
}).catch(function(error) {
errorMessage = error.toString();
if (errorMessage.indexOf("invalid opcode") > 0){
assert(true, "Call should not be allowed - error as expected"); }
else{
assert(true, "Call should not be allowed - wrong message");
}
});
});
});
