Use TestUp with EVM in JS

readme.md

Run EVM tests with TestUp

This is short explanation of how tests scripts and helpers might look.

evm.spec.js

import {initEvm, checkpoint} from './helpers';

export default ({describe, it, use, each}) => {
  describe('Subject', () => {
    // Initialize VM and put it into test context
    use(initEvm({
      accounts: {
        alice: {balance: '1 eth'},
        bob: {balance: 0},
      },
    }))
    
    // Make each test to add a checkpoint and to rollback
    each(checkpoint)
    
    // Run test and change the state
    it('test', async (test, ctx) => {
        const {alice, bob} = ctx.accounts

        await alice.transfer('0.5 eth', bob)
        const balance = await bob.getBalance('eth')

        assert.equal(balance, '5', 'Balance is 5')
      
        test.end()
    })
    
    // Run test with initial state, where Alice has 5 ethers and Bob has zero.
    it('test', async (test, ctx) => {
        const {alice, bob} = ctx.accounts

        const aliceBalance = await alice.getBalance('eth')
        const bobBalance = await bob.getBalance('eth')

        assert.equal(aliceBalance, '5', 'Alice balance is 5')
        assert.equal(bobBalance, '0', 'Bob balance is 0')
      
        test.end()
    })
  })
}

helpers.js

// Initialize EVM with a given params
export function initEvm(params) {
  async function (ctx, next) {
    const {evmModule} = ctx.specOpts
    const {default: VM, StateManager} = await import(evmModule)
    
    const state = new StateManager()
    const evm = await VM.create({state})
    
    const accounts = await createAccountsSomeHow(evm, params)
    
    // Put to context new vaalues `evm`, `state` and `accounts`.
    // This call equals to Object.assign(Object.create(ctx), {evm, state, accounts})
    await next({
      evm,
      state,
      accounts,
    })
  }
}

// Add checkpoint and rollback after test end
export async function checkpoint(ctx, next) {
  const {evm} = ctx
  const state = evm.pStateManager
  try {
    await state.checkpoint()
    await next()
  }
  finally {
    await state.rollback()
  }
}