Simulating the passage of time with testrpc

Question

Any tips on how to simulate real network conditions on the testrpc testing client using truffle? I have some functions that look at blocknumber and try to deal with passing time. Has anyone come up with a good way to test these kind of things?

I'm wondering if just calling some null transactions in a loop with increase the block number accordingly. Any info on the inner workings of these things would be appreciated.

Answer 1

By default, every transaction called in testrpc is immediately mined and the block height will increase. The time it takes to mine each block can be set as a command line option when starting testrpc using -b or --blocktime

In addition, testrpc provides a custom rpc method you can use to manipulate the block height:

evm_mine : Force a block to be mined. Takes no parameters. Mines a block independent of whether or not mining is started or stopped.

Testrpc's custom methods can be called from web3 using web3.currentProvider.sendAsync() like so:

web3.currentProvider.sendAsync({
  jsonrpc: "2.0",
  method: "evm_mine",
  id: 12345
}, function(err, result) {
  // this is your callback
});

Answer 2

I wrote an entire article about this: Writing Accurate Time-Dependent Truffle Tests.

TLDR;

While I strongly advise to check it out (there's some subtleties involved), here's the short story.

Either do npm install ganache-time-traveler or copy-paste the following in your project:

const advanceBlockAtTime = (time) => {
  return new Promise((resolve, reject) => {
    web3.currentProvider.send(
      {
        jsonrpc: "2.0",
        method: "evm_mine",
        params: [time],
        id: new Date().getTime(),
      },
      (err, _) => {
        if (err) {
          return reject(err);
        }
        const newBlockHash = web3.eth.getBlock("latest").hash;

        return resolve(newBlockHash);
      },
    );
  });
};

Answer 3

I found a way to write time precise test by using own wrapper:

const { time } = require('openzeppelin-test-helpers');    

async function timeIncreaseTo (seconds) {
    const delay = 1000 - new Date().getMilliseconds();
    await new Promise(resolve => setTimeout(resolve, delay));
    await time.increaseTo(seconds);
}

I noticed that Ganache-cli switches EVM seconds exactly when host switches seconds. So I added waiting for new second and then increase time on EVM. So, I have 1 exact second to perform all necessary transactions and calls until EVM time will be switched.

Usage:

const { time } = require('openzeppelin-test-helpers');    

// Skip 10 sec to have exact 1 second
await timeIncreaseTo((await time.latest()).addn(10));

await this.contract.deposit(1000000);
const timeDeposited = await time.latest();

// Skip 1 year
await timeIncreaseTo(timeDeposited.add(time.duration.years(1)).subn(1));

expect(await this.contract.balanceOf(wallet)).to.be.bignumber.equal('1060000'); // +6%
await this.contract.withdrawAll();