For instance I'm running testcase for a smart contract and it's test function has required validation.

function test(uint _id) public pure returns(bool){
    require(_id == 0 ,"not valid!");
    return true;

But when I execute the test case it throwing an error

AssertionError: Error: VM Exception while processing transaction: revert

Test cases:

it("Adding test into blockchain", async () => {                               

    const result = await Instance.test(1);                        


it("Adding zero Id test into blockchain", async () => {                               

    const result = await Instance.test(0);                        

    //TODO: get error message   
  • what's your test block?
    – Badr Bellaj
    Jul 13, 2018 at 8:25
  • @BadrBellaj: question updated!
    – Hina
    Jul 13, 2018 at 8:32

2 Answers 2


Of course it will fire an exception

you have in the first test require(_id == 0 ,"not valid!");

and you feed it _id=1 (test(1)) therefore an exception will be raised.

either test with test(0)


check try/catch the exception as follow :

try {
     await Instance.test(1); 
        } catch (error) {
            Error = error;
        assert.notEqual(Error, undefined, 'Error must be thrown');
        assert.isAbove(Error.message.search('VM Exception while processing transaction: revert'), -1, 'Error: VM Exception while processing transaction: revert');

  • either test with test(0), but I want to create negative test(s) to make sure smart contract would handle the things appropriately. check try/catch the exception any example would be really helpful, currently I added catch block, though it gives an exception.
    – Hina
    Jul 13, 2018 at 10:33
  • I also tried to make library like this but seems import having issue with truffle.. don't know how other implemented.
    – Hina
    Jul 13, 2018 at 10:38
  • check the try/catch block i've proposed
    – Badr Bellaj
    Jul 13, 2018 at 10:40
  • 1
    what's awful in it? :p you raise an error and you check the message nothing harmfull
    – Badr Bellaj
    Jul 13, 2018 at 10:52
  • 2
    What if you have a stack of require statements and want to test which one triggered during a test. Without the message it seems impossible. Also, if you can't get the require message, what purpose does it even serve?
    – Justin
    Jul 13, 2018 at 14:59

you can either use truffle-assertions with

npm install truffle-assertions

in your test code

const truffleAssert = require('truffle-assertions');
await truffleAssert.reverts(Instance.test(1));

or you can use a simple try catch with

    try {
        await Instance.test(1);
    } catch(err) {
        Error = err
    assert.equal(Error.reason, 'not valid!');

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