Branch a Truffle test into various Ganache blockchain states

Question

I am currently testing a contract that can evolve in different ways, depending on the interaction between parties. But all these possible scenarios share the same initialization.

So, the question I have is the following. When I am writing a test for this contract in Truffle/Ganache, is it possible to run a single chain until the decision point, then create several copies of the test blockchain state, one for each possible scenario?

I know that Ganache offers the evm_snapshot and evm_revert RPC calls. But it is not clear to me how to use them and how it interacts with Truffle and Mocha.

Also, can I use nested contract directives, as we can nest describe in Mocha?

Ideally I would like to do something like this:

var Contract = artifacts.require("./Contract.sol");

contract('Contract', function(accounts) {
  beforeEach(async function() {
    // launch contract
    let contract = await Contract
        .new({ from: accounts[2], gas: 2000000 });

    // let users interact here
    // ...
  });

  contract('Agreement', function(accounts) {
    it('Payment is processed', async function() {
      // test that payment was processed
    });
  });

  contract('Disagreement, see who is right', function(accounts) {

    contract('Alice right', function(accounts) {
      it('Punish Bob', async function() {
        // show that Alice is right and punish Bob
      });
    });
    contract('Alice right', function(accounts) {
      it('Punish Alice', async function() {
        // show that Bob is right and punish Alice
      });
    });
  });
}

You see that we are testing three different outcomes, but they share the same initialization. I would like to avoid starting three fresh chains, one for each test. Is it possible and how one does it?

Answer 1

After testing here, I realized that the above code works in the following sense. Truffle will automatically snapshot and revert the two tests above. Some important observations:

• One should not nest the directive contracts inside one another in this case, since there is only one contract being tested. We should instead use describes inside contract.
• Using before does not work properly with snapshots. One should instead use beforeEach as stated in the question.
• In the code above I forgot the keyword async in some function declarations. It should be present in each describe and it directive.