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Fadroma Guide: Mocknet

Testing the production builds of smart contracts can be slow and awkward. Testnets are permanent and public; devnets can be temporary, but transactions are still throttled by the block rate.

Mocknet is a lightweight functioning mock of a CosmWasm-capable platform, structured as an implementation of the Fadroma Chain API. It emulates the APIs that a CosmWasm contract expects to see when running in production, on top of the JavaScript engine's built-in WebAssembly runtime.

This way, you can run your real smart contracts without a real blockchain, and quickly test their user-facing functionality and interoperation in a customizable environment.

Table of contents

Getting started with mocknet

You can interact with a mocknet from TypeScript, the same way you interact with any other chain - through the Fadroma Client API.

import { Mocknet } from '@fadroma/agent'
let chain = new Mocknet.Chain()
let agent = await chain.getAgent()

import { Chain, Agent, Mocknet } from '@fadroma/agent'
assert.ok(chain instanceof Chain)
assert.ok(agent instanceof Agent)
assert.ok(agent instanceof Mocknet.Agent)

When creating a mocknet, the block height starts at 0. You can increment it manually to represent the passing of block time.

Native token balances also start at 0. You can give native tokens to agents by setting the Mocknet#balances property:

assert.equal(await chain.height, 0)

chain.balances[agent.address] = 1000
assert.equal(await chain.getBalance(agent.address), 1000)

assert.equal(agent.defaultDenom, chain.defaultDenom)
assert.ok(await agent.account)
assert.ok(!await agent.send())
assert.ok(!await agent.sendMany())

Testing contracts on mocknet

Uploading WASM blob will return the expected monotonously incrementing code ID...

import { pathToFileURL } from 'url'
import { examples } from '../fixtures/'

assert.equal(chain.lastCodeId, 0)

const uploaded_a = await agent.upload(examples['KV'].data.load(), examples['KV'])
assert.equal(uploaded_a.codeId, 1)
assert.equal(chain.lastCodeId, 1)

const uploaded_b = await agent.upload(examples['Legacy'].data.load(), examples['Legacy'])
assert.equal(uploaded_b.codeId, 2)
assert.equal(chain.lastCodeId, 2)

...which you can use to instantiate the contract.

const contract_a = uploaded_a.instance({ agent, name: 'kv', initMsg: { fail: false } })
const client_a = await contract_a.deployed

const contract_b = uploaded_b.instance({ agent, name: 'legacy', initMsg: { fail: false } })
const client_b = await contract_b.deployed

  await client_a.query({get: {key: "foo"}}),
  [null, null] // value returned from the contract

assert.ok(await client_a.execute({set: {key: "foo", value: "bar"}}))

const [data, meta] = await client_a.query({get: {key: "foo"} })
assert.equal(data, 'bar')

await chain.getLabel(client_a.address)
await chain.getHash(client_a.address)
await chain.getCodeId(client_a.codeHash)

Backwards compatibility

Mocknet supports contracts compiled for CosmWasm 0.x or 1.x.

assert.equal(chain.contracts[contract_a.address].cwVersion, '1.x')
assert.equal(chain.contracts[contract_b.address].cwVersion, '0.x')


Currently, Mocknet is not stateful: it only exists for the duration of the script run.

You can instantiate Mocknet with pre-uploaded contracts:

chain = new Mocknet.Chain({
  uploads: {
    1:   new Uint8Array(),
    234: new Uint8Array()
    567: new Uint8Array()

assert.equal(chain.lastCodeId, 567)

import assert from 'node:assert'