JS Testing API Reference

⚠️ Required: Your project must follow the required structure and it must be initialized to use the following functions.

Accounts

`getAccountAddress`

Resolves name alias to a Flow address (0x prefixed) under the following conditions:

If an account with a specific name has not been previously accessed, the framework will create a new one and then store it under the provided alias.
Next time when you call this method, it will grab exactly the same account. This allows you to create several accounts up-front and then use them throughout your code, without worrying that accounts match or trying to store and manage specific addresses.

Arguments

Name	Type	Description
`alias`	string	The alias to reference or create.

Returns

Type	Description
Address	`0x` prefixed address of aliased account

Usage

import {getAccountAddress} from "@onflow/flow-js-testing"
const main = async () => {
  const Alice = await getAccountAddress("Alice")
  console.log({Alice})
}
main()

`createAccount({name, keys})`

In some cases, you may wish to manually create an account with a particular set of private keys

Options

Pass in the following as a single object with the following keys.

Key	Type	Required	Description
`name`	string	No	human-readable name to be associated with created account (will be used for address lookup within getAccountAddress)
`keys`	[KeyObject or PublicKey]	No	An array of KeyObjects or PublicKeys to be added to the account upon creation (defaults to the universal private key)

📣 if name field not provided, the account address will not be cached and you will be unable to look it up using getAccountAddress.

Returns

Type	Description
Address	`0x` prefixed address of created account

Contracts

`deployContractByName(props)`

Deploys contract code located inside a Cadence file. Returns the transaction result.

Arguments

Props object accepts the following fields:

Name	Type	Optional	Description
`name`	string		name of the file in `contracts` folder (with `.cdc` extension) and name of the contract (please note those should be the same)
`to`	Address	✅	(optional) account address, where contract will be deployed. If this is not specified, framework will create new account with randomized alias.
`addressMap`	AddressMap	✅	(optional) object to use for address mapping of existing deployed contracts
`args`	[Any]	✅	(optional) arguments, which will be passed to contract initializer. (optional) if template does not expect any arguments.
`update`	boolean	✅	(optional) whether to update deployed contract. Default: `false`
`transformers`	[CadenceTransformer]	✅	(optional) an array of operators to modify the code, before submitting it to network

Returns

Type	Description
ResponseObject	Result of the deploying transaction.

Usage

import path from "path";
import { init, emulator, deployContractByName } from "@onflow/flow-js-testing";
const main = async () => {
  const basePath = path.resolve(__dirname, "../cadence");
  await init(basePath);
  await emulator.start();
  // We will deploy our contract to the address that corresponds to "Alice" alias
  const to = await getAccountAddress("Alice");
  // We assume there is a file on "../cadence/contracts/Wallet.cdc" path
  const name = "Wallet";
  // Arguments will be processed and type matched in the same order as they are specified
  // inside of a contract template
  const args = [1337, "Hello", { name: "Alice" }];
  const [deploymentResult, err] = await deployContractByName({ to, name });
  console.log({ deploymentResult }, { err });
  }
  await emulator.stop();
};
main();

In a bit more rare case you would want to deploy contract code not from existing template file, but rather from string representation of it. deployContract method will help you achieve this.

`deployContract(props)`

Deploys contract code specified as string. Returns the transaction result.

Arguments

Props object accepts the following fields:

Name	Type	Optional	Description
`contractCode`	string		string representation of contract
`name`	string		name of the contract to be deployed. Should be the same as the name of the contract provided in `contractCode`
`to`	Address	✅	account address, where contract will be deployed. If this is not specified, framework will create new account with randomized alias.
`addressMap`	AddressMap	✅	object to use for import resolver. Default: `{}`
`args`	[Any]	✅	arguments, which will be passed to contract initializer. Default: `[]`
`update`	boolean	✅	whether to update deployed contract. Default: `false`
`transformers`	[CadenceTransformer]	✅	an array of operators to modify the code, before submitting it to network

Returns

Type	Description
ResponseObject	Result of the deploying transaction.

Usage

import path from "path"
import {
  init,
  emulator,
  getAccountAddress,
  deployContract,
  executeScript,
} from "@onflow/flow-js-testing"
;(async () => {
  const basePath = path.resolve(__dirname, "../cadence")
  await init(basePath)
  await emulator.start()
  // We can specify, which account will hold the contract
  const to = await getAccountAddress("Alice")
  const name = "Wallet"
  const code = `
        pub contract Wallet{
            pub let balance: UInt
            init(balance: UInt){
              self.balance = balance
            }
        }
    `
  const args = [1337]
  await deployContract({to, name, code, args})
  const [balance, err] = await executeScript({
    code: `
      import Wallet from 0x01
      pub fun main(): UInt{
        return Wallet.balance
      }
    `,
  })
  console.log({balance}, {err})
  await emulator.stop()
})()

While framework have automatic import resolver for Contracts you might want to know where it's currently deployed. We provide a method getContractAddress for this.

`getContractAddress(name)`

Returns address of the account where the contract is currently deployed.

Arguments

Name	Type	Description
`name`	string	name of the contract

Returns

Type	Description
Address	`0x` prefixed address

Usage

import path from "path"
import {init, emulator, deployContractByName, getContractAddress} from "../src"
;(async () => {
  const basePath = path.resolve(__dirname, "./cadence")
  await init(basePath)
  await emulator.start()
  // if we omit "to" it will be deployed to Service Account
  // but let's pretend we don't know where it will be deployed :)
  await deployContractByName({name: "Hello"})
  const contractAddress = await getContractAddress("Hello")
  console.log({contractAddress})
  await emulator.stop()
})()

📣 Framework does not support contracts with identical names deployed to different accounts. While you can deploy contract to a new address, the internal system, which tracks where contracts are deployed, will only store last address.

Cryptography

`pubFlowKey(keyObject)`

The pubFlowKey method exported by Flow JS Testing Library will generate an RLP-encoded public key given a private key, hashing algorithm, signing algorithm, and key weight.

Name	Type	Optional	Description
`keyObject`	KeyObject	✅	an object containing a private key & the key's hashing/signing information

If keyObject is not provided, Flow JS Testing will default to the universal private key.

Returns

Type	Description
Buffer	RLP-encoded public key

Usage

import {pubFlowKey} from "@onflow/flow-js-testing"
const key = {
  privateKey: "a1b2c3", // private key as hex string
  hashAlgorithm: HashAlgorithm.SHA3_256,
  signatureAlgorithm: SignatureAlgorithm.ECDSA_P256,
  weight: 1000
}
const pubKey = await pubFlowKey(key) // public key generated from keyObject provided
const genericPubKey = await pubFlowKey() // public key generated from universal private key/service key

`signUserMessage(msgHex, signer, domainTag)`

The signUserMessage method will produce a user signature of some arbitrary data using a particular signer.

Arguments

Name	Type	Optional	Description
`msgHex`	string or Buffer		a hex-encoded string or Buffer which will be used to generate the signature
`signer`	Address or SignerInfo	✅	Address or SignerInfo object representing user to generate this signature for (default: universal private key)
`domainTag`	string	✅	Domain separation tag provided as a utf-8 encoded string (default: no domain separation tag). See more about domain tags here.

Returns

Type	Description
SignatureObject	An object representing the signature for the message & account/keyId which signed for this message

Usage

import {signUserMessage, getAccountAddress} from "@onflow/flow-js-testing"
const Alice = await getAccountAddress("Alice")
const msgHex = "a1b2c3"
const signature = await generateUserSignature(msgHex, Alice)

`verifyUserSigntatures(msgHex, signatures, domainTag)`

Used to verify signatures generated by signUserMessage. This function takes an array of signatures and verifies that the total key weight sums to >= 1000 and that these signatures are valid.

Arguments

Name	Type	Optional	Description
`msgHex`	string		the message which the provided signatures correspond to provided as a hex-encoded string or Buffer
`signatures`	[SignatureObject]		An array of SignatureObjects which will be verified against this message
`domainTag`	string	✅	Domain separation tag provided as a utf-8 encoded string (default: no domain separation tag). See more about domain tags here.

Returns

This method returns an object with the following keys:

Type	Description
boolean	Returns true if signatures are valid and total weight >= 1000

Usage

import {
  signUserMessage,
  verifyUserSignatures,
  getAccountAddress,
} from "@onflow/flow-js-testing"
const Alice = await getAccountAddress("Alice")
const msgHex = "a1b2c3"
const signature = await generateUserSignature(msgHex, Alice)
console.log(await verifyUserSignatures(msgHex, Alice)) // true
const Bob = await getAccountAddress("Bob")
console.log(await verifyUserSignatures(msgHex, Bob)) // false

Emulator

Flow Javascript Testing Framework exposes emulator singleton allowing you to run and stop emulator instance programmatically. There are two methods available on it.

`emulator.start(options)`

Starts emulator on a specified port. Returns Promise.

Arguments

Name	Type	Optional	Description
`options`	EmulatorOptions	✅	an object containing options for starting the emulator

EmulatorOptions

Key	Type	Optional	Description
`logging`	boolean	✅	whether log messages from emulator shall be added to the output (default: false)
`flags`	string	✅	custom command-line flags to supply to the emulator (default: no flags)
`adminPort`	number	✅	override the port which the emulator will run the admin server on (default: auto)
`restPort`	number	✅	override the port which the emulator will run the REST server on (default: auto)
`grpcPort`	number	✅	override the port which the emulator will run the GRPC server on (default: auto)

Returns

Type	Description
Promise	Promise, which resolves to true if emulator started successfully

Usage

import path from "path"
import {emulator, init} from "../src"
;(async () => {
  const basePath = path.resolve(__dirname, "../cadence")
  await init(basePath)
  // Start emulator instance on port 8080
  await emulator.start()
  console.log("emulator is working")
  // Stop running emulator
  await emulator.stop()
  console.log("emulator has been stopped")
})()

`emulator.stop()`

Stops emulator instance. Returns Promise.

Arguments

This method does not expect any arguments.

Returns

Type	Description
Promise	Promise, which resolves to true if emulator stopped without issues

Usage

import {emulator, init} from "@onflow/flow-js-testing"
describe("test setup", () => {
  // Instantiate emulator and path to Cadence files
  beforeEach(async () => {
    const basePath = path.resolve(__dirname, "../cadence")
    await init(basePath)
    await emulator.start()
  })
  // Stop emulator, so it could be restarted
  afterEach(async () => {
    await emulator.stop()
  })
})

`emulator.setLogging(newState)`

Set logging flag on emulator, allowing to temporally enable/disable logging.

Arguments

Name	Type	Description
`newState`	boolean	Enable/disable logging

Returns

Method does not return anything.

Usage

import path from "path"
import {emulator, init} from "@onflow/flow-js-testing"
describe("test setup", () => {
  // Instantiate emulator and path to Cadence files
  beforeEach(async () => {
    const basePath = path.resolve(__dirname, "../cadence")
    await init(basePath)
    await emulator.start()
  })
  // Stop emulator, so it could be restarted
  afterEach(async () => {
    await emulator.stop()
  })
  test("basic test", async () => {
    // Turn on logging from begining
    emulator.setLogging(true)
    // some asserts and interactions
    // Turn off logging for later calls
    emulator.setLogging(false)
    // more asserts and interactions here
  })
})

FLOW Management

Some actions on the network will require account to have certain amount of FLOW token - transaction and storage fees, account creation, etc.

Framework provides a method to query balance with getFlowBalance and mint new tokens via mintFlow. You can find information how to use them below.

`getFlowBalance(address)`

Fetch current FlowToken balance of account specified by address

Arguments

Name	Type	Description
`address`	Address	address of the account to check

Returns

Type	Description
string	UFix64 amount of FLOW tokens stored in account storage represented as string

Usage

import {
  init,
  emulator,
  getAccountAddress,
  getFlowBalance,
} from "@onflow/flow-js-testing"
const main = async () => {
  const basePath = path.resolve(__dirname, "../cadence")
  await init(basePath)
  await emulator.start()
  const Alice = await getAccountAddress("Alice")
  const [result, error] = await getFlowBalance(Alice)
  console.log({result}, {error})
  await emulator.stop()
}
main()

`mintFlow(recipient, amount)`

Sends transaction to mint specified amount of FLOW token and send it to recipient.

⚠️ Required: Framework shall be initialized with init method for this method to work.

Arguments

Name	Type	Description
`recipient`	Address	address of the account to check
`amount`	string	UFix64 amount of FLOW tokens to mint and send to recipient

Returns

Type	Description
ResponseObject	Transaction result

Usage

import path from "path"
import {
  init,
  emulator,
  getAccountAddress,
  getFlowBalance,
  mintFlow,
} from "../src"
;(async () => {
  const basePath = path.resolve(__dirname, "./cadence")
  await init(basePath)
  await emulator.start()
  // Get address for account with alias "Alice"
  const Alice = await getAccountAddress("Alice")
  // Get initial balance
  const [initialBalance] = await getFlowBalance(Alice)
  console.log(initialBalance)
  // Add 1.0 FLOW tokens to Alice account
  await mintFlow(Alice, "1.0")
  // Check updated balance
  const updatedBalance = await getFlowBalance(Alice)
  console.log({updatedBalance})
  await emulator.stop()
})()

Init

For Framework to operate properly you need to initialize it first. You can do it with provided init method.

init( basePath, options)

Initializes framework variables.

Arguments

Name	Type	Optional	Description
`bastPath`	string		path to the folder holding all Cadence template files
`options`	object	✅	options object to use during initialization

Options

Name	Type	Optional	Description
`pkey`		✅	private key for service account

Returns

Type	Description
Promise	Promise, which resolves to true if framework was initialized properly

Usage

import path from "path"
import {init} from "@onflow/flow-js-testing"
describe("test setup", () => {
  beforeEach(async () => {
    const basePath = path.resolve(__dirname, "../cadence")
    await init(basePath)
    // alternatively you can pass specific port
    // await init(basePath, {port: 8085})
  })
})

Environment

`getBlockOffset()`

Returns current block offset - amount of blocks added on top of real current block height.

Returns

Type	Description
string	number representing amount of blocks added on top of real current block (encoded as string)

Usage

import path from "path"
import {init, emulator, getBlockOffset} from "@onflow/flow-js-testing"
const main = async () => {
  const basePath = path.resolve(__dirname, "../cadence")
  init(basePath)
  await emulator.start()
  const [blockOffset, err] = await getBlockOffset()
  console.log({blockOffset}, {err})
  await emulator.stop()
}
main()

`setBlockOffset(offset)`

Returns current block offset - amount of blocks added on top of real current block height.

Arguments

Name	Type	Description

Returns

Type	Description
number	number representing amount of blocks added on top of real current block height

Usage

import path from "path"
import {
  init,
  emulator,
  executeScript,
  getBlockOffset,
  setBlockOffset,
  sendTransaction,
} from "@onflow/flow-js-testing"
const main = async () => {
  const basePath = path.resolve(__dirname, "../cadence")
  init(basePath)
  await emulator.start()
  // Offset current block height by 42
  await setBlockOffset(42)
  const [blockOffset, err] = await getBlockOffset()
  console.log({blockOffset}, {err})
  // "getCurrentBlock().height" in your Cadence code will be replaced by Manager to a mocked value
  const code = `
    pub fun main(): UInt64 {
      return getCurrentBlock().height
    }
  `
  const [result, error] = await executeScript({code})
  console.log({result}, {error})
  await emulator.stop()
}
main()

`getTimestampOffset()`

Returns current timestamp offset - amount of seconds added on top of real current timestamp.

Returns

Type	Description
number	number representing amount of seconds added on top of real current timestamp

Usage

import path from "path"
import {init, emulator, getTimestampOffset} from "@onflow/flow-js-testing"
const main = async () => {
  const basePath = path.resolve(__dirname, "../cadence")
  init(basePath)
  await emulator.start()
  const [timestampOffset, err] = await getTimestampOffset()
  console.log({timestampOffset}, {err})
  await emulator.stop()
}
main()

`setTimestampOffset(offset)`

Returns current timestamp offset - amount of seconds added on top of real current timestamp.

Arguments

Name	Type	Description

Returns

Type	Description
number	number representing amount of seconds added on top of real current timestamp

Usage

import path from "path"
import {
  init,
  emulator,
  executeScript,
  getTimestampOffset,
  setTimestampOffset,
  sendTransaction,
} from "@onflow/flow-js-testing"
const main = async () => {
  const basePath = path.resolve(__dirname, "../cadence")
  init(basePath)
  await emulator.start()
  // Offset current timestamp by 10s
  await setTimestampOffset(10)
  const [timestampOffset, err] = await getTimestampOffset()
  console.log({timestampOffset}, {err})
  // "getCurrentBlock().timestamp" in your Cadence code will be replaced by Manager to a mocked value
  const code = `
    pub fun main(): UInt64 {
      return getCurrentBlock().timestamp
    }
  `
  const [result, error] = await executeScript({code})
  console.log({result}, {error})
  await emulator.stop()
}
main()

Jest Helpers

In order to simplify the process even further we've created several Jest-based methods, which will help you to catch thrown errors and ensure your code works as intended.

`shallPass(ix)`

Ensure transaction does not throw and sealed.

Arguments

Name	Type	Description
`ix`	Interaction	interaction, either in form of a Promise or function

Returns

Type	Description
ResponseObject	Transaction result

Usage

import path from "path"
import {
  init,
  emulator,
  shallPass,
  sendTransaction,
  getAccountAddress,
} from "js-testing-framework"
// We need to set timeout for a higher number, cause some interactions might need more time
jest.setTimeout(10000)
describe("interactions - sendTransaction", () => {
  // Instantiate emulator and path to Cadence files
  beforeEach(async () => {
    const basePath = path.resolve(__dirname, "./cadence")
    await init(basePath)
    return emulator.start()
  })
  // Stop emulator, so it could be restarted
  afterEach(async () => {
    return emulator.stop()
  })
  test("basic transaction", async () => {
    const code = `
      transaction(message: String){
        prepare(singer: AuthAccount){
          log(message)
        }
      }
    `
    const Alice = await getAccountAddress("Alice")
    const signers = [Alice]
    const args = ["Hello, Cadence"]
    const [txResult, error] = await shallPass(
      sendTransaction({
        code,
        signers,
        args,
      })
    )
    // Transaction result will hold status, events and error message
    console.log({txResult}, {error})
  })
})

shallRevert(ix, message)

Ensure interaction throws an error. Can test for specific error messages or catch any error message if message is not provided. Returns Promise, which contains result, when resolved.

Arguments

Name	Type	Description
`ix`	Interaction	transaction, either in form of a Promise or function
`message` (optional)	`string` or `RegExp`	expected error message provided as either a string equality or regular expression to match, matches any error by default

Returns

Type	Description
ResponseObject	Transaction result

Usage

import path from "path"
import {
  init,
  emulator,
  shallPass,
  sendTransaction,
  getAccountAddress,
} from "js-testing-framework"
// We need to set timeout for a higher number, cause some interactions might need more time
jest.setTimeout(10000)
describe("interactions - sendTransaction", () => {
  // Instantiate emulator and path to Cadence files
  beforeEach(async () => {
    const basePath = path.resolve(__dirname, "./cadence")
    await init(basePath)
    return emulator.start()
  })
  // Stop emulator, so it could be restarted
  afterEach(async () => {
    return emulator.stop()
  })
  test("basic transaction", async () => {
    const code = `
      transaction(message: String){
        prepare(singer: AuthAccount){
          panic("You shall not pass!")
        }
      }
    `
    const Alice = await getAccountAddress("Alice")
    const signers = [Alice]
    const args = ["Hello, Cadence"]
    // Catch any cadence error
    let [txResult, error] = await shallRevert(
      sendTransaction({
        code,
        signers,
        args,
      })
    )
    // Catch only specific panic message
    let [txResult2, error2] = await shallRevert(
      sendTransaction({
        code,
        signers,
        args,
      }),
      "You shall not pass!"
    )
    // Transaction result will hold status, events and error message
    console.log({txResult}, {error})
  })
})

shallResolve(ix)

Ensure interaction resolves without throwing errors.

Arguments

Name	Type	Description
`ix`	Interaction	interaction, either in form of a Promise or function

Returns

Type	Description
InteractionResult	Interaction result

Usage

import path from "path"
import {init, emulator, shallPass, executeScript} from "js-testing-framework"
// We need to set timeout for a higher number, cause some interactions might need more time
jest.setTimeout(10000)
describe("interactions - sendTransaction", () => {
  // Instantiate emulator and path to Cadence files
  beforeEach(async () => {
    const basePath = path.resolve(__dirname, "./cadence")
    await init(basePath)
    return emulator.start()
  })
  // Stop emulator, so it could be restarted
  afterEach(async () => {
    return emulator.stop()
  })
  test("basic script", async () => {
    const code = `
      pub fun main():Int{
        return 42
      }
    `
    const [result, error] = await shallResolve(
      executeScript({
        code,
      })
    )
    expect(result).toBe(42)
    expect(error).toBe(null)
  })
})

Scripts

It is often the case that you need to query current state of the network. For example, to check balance of the account, read public value of the contract or ensure that user has specific resource in their storage.

We abstract this interaction into single method called executeScript. Method have 2 different signatures.

⚠️ Required: Your project must follow the required structure it must be initialized to use the following functions.

`executeScript(props)`

Provides explicit control over how you pass values.

Arguments

props object accepts following fields:

Name	Type	Optional	Description
`code`	string	✅	string representation of Cadence script
`name`	string	✅	name of the file in `scripts` folder to use (sans `.cdc` extension)
`args`	[any]	✅	an array of arguments to pass to script. Optional if script does not expect any arguments.
`transformers`	[CadenceTransformer]	✅	an array of operators to modify the code, before submitting it to network

⚠️ Required: Either code or name field shall be specified. Method will throw an error if both of them are empty. If name field provided, framework will source code from file and override value passed via code field.

Returns

Type	Description
ResponseObject	Script result

Usage

import path from "path"
import {init, emulator, executeScript} from "@onflow/flow-js-testing"
const main = async () => {
  const basePath = path.resolve(__dirname, "../cadence")
  // Init framework
  init(basePath)
  // Start emulator
  await emulator.start()
  // Define code and arguments we want to pass
  const code = `
    pub fun main(message: String): Int{
      log(message)
      return 42
    }
  `
  const args = ["Hello, from Cadence"]
  const [result, error, logs] = await executeScript({code, args})
  console.log({result}, {error}, {logs})
  // Stop emulator instance
  await emulator.stop()
}
main()

`executeScript(name: string, args: [any])`

This signature provides simplified way of executing a script, since most of the time you will utilize existing Cadence files.

Arguments

Name	Type	Optional	Description
`name`	string		name of the file in `scripts` folder to use (sans `.cdc` extension)
`args`	[any]	✅	an array of arguments to pass to script. Optional if scripts don't expect any arguments. Default: `[]`

Returns

Type	Description
ResponseObject	Script result

Usage

import path from "path"
import {init, emulator, executeScript} from "@onflow/flow-js-testing"
const main = async () => {
  const basePath = path.resolve(__dirname, "../cadence")
  // Init framework
  init(basePath)
  // Start emulator
  await emulator.start()
  // Define arguments we want to pass
  const args = ["Hello, from Cadence"]
  // We assume there is a file `scripts/log-message.cdc` under base path
  const [result, error, logs] = await executeScript("log-message", args)
  console.log({result}, {error}, {logs})
  await emulator.stop()
}
main()

Transactions

Another common case is interactions that mutate network state - sending tokens from one account to another, minting new NFT, etc. Framework provides sendTransaction method to achieve this. This method have 2 different signatures.

⚠️ Required: Your project must follow the required structure it must be initialized to use the following functions.

`sendTransaction(props)`

Send transaction to network. Provides explicit control over how you pass values.

Arguments

props object accepts following fields:

Name	Type	Optional	Description
`code`	string	✅	string representation of Cadence transaction
`name`	string	✅	name of the file in `transaction` folder to use (sans `.cdc` extension)
`args`	[any]	✅	an array of arguments to pass to transaction. Optional if transaction does not expect any arguments.
`signers`	[Address or SignerInfo]	✅	an array of Address or SignerInfo objects representing transaction autorizers
`addressMap`	AddressMap	✅	name/address map to use as lookup table for addresses in import statements
`transformers`	[CadenceTransformer]	✅	an array of operators to modify the code, before submitting it to network

⚠️ Required: Either code or name field shall be specified. Method will throw an error if both of them are empty. If name field provided, framework will source code from file and override value passed via code field.

📣 if signers field not provided, service account will be used to authorize the transaction.

📣 Pass addressMap only in cases, when you would want to override deployed contract. Otherwide imports can be resolved automatically without explicitly passing them via addressMap field

Usage

import path from "path"
import {
  init,
  emulator,
  sendTransaction,
  getAccountAddress,
} from "@onflow/flow-js-testing"
const main = async () => {
  const basePath = path.resolve(__dirname, "../cadence")
  // Init framework
  await init(basePath)
  // Start emulator
  await emulator.start()
  // Define code and arguments we want to pass
  const code = `
    transaction(message: String){
      prepare(signer: AuthAccount){
        log(message)
      }
    }
  `
  const args = ["Hello, from Cadence"]
  const Alice = await getAccountAddress("Alice")
  const signers = [Alice]
  const [result, error, logs] = await sendTransaction({code, args, signers})
  console.log({result}, {error}, {logs})
  // Stop emulator instance
  await emulator.stop()
}
main()

`sendTransaction(name, signers, args)`

This signature provides simplified way to send a transaction, since most of the time you will utilize existing Cadence files.

Name	Type	Optional	Description
`name`	string	✅	name of the file in `transaction` folder to use (sans `.cdc` extension)
`args`	[any]	✅	an array of arguments to pass to transaction. Optional if transaction does not expect any arguments.
`signers`	[Address or SignerInfoObject]	✅	an array of Address or array of SignerInfoObject representing transaction autorizers

Usage

import path from "path"
import {
  init,
  emulator,
  sendTransaction,
  shallPass,
} from "@onflow/flow-js-testing"
const main = async () => {
  const basePath = path.resolve(__dirname, "../cadence")
  // Init framework
  await init(basePath)
  // Start emulator
  await emulator.start()
  // Define arguments we want to pass
  const args = ["Hello, Cadence"]
  const [result, error, logs] = await shallPass(
    sendTransaction("log-message", [], args)
  )
  console.log({result}, {error}, {logs})
  // Stop the emulator instance
  await emulator.stop()
}
main()

Templates

The philosophy behind Flow JS Testing Framework is to be a set of helper methods. They can be used in opinionated way, envisioned by Flow Team. Or they can work as building blocks, allowing developers to build their own testing solution as they see fit.

Following methods used inside other framework methods, but we feel encouraged to list them here as well.

`getTemplate(file, addressMap, byAddress)`

Returns Cadence template as string with addresses replaced using addressMap

Name	Type	Optional	Description
`file`	string		relative (to the place from where the script was called) or absolute path to the file containing the code
`addressMap`	AddressMap	✅	object to use for address mapping of existing deployed contracts. Default: `{}`
`byAddress`	boolean	✅	whether addressMap is `{name:address}` or `{address:address}` type. Default: `false`

Returns

Type	Description
string	content of a specified file

Usage

import path from "path"
import {init, getTemplate} from "@onflow/flow-js-testing"
const main = async () => {
  const basePath = path.resolve(__dirname, "../cadence")
  await init(basePath)
  const template = await getTemplate("../cadence/scripts/get-name.cdc")
  console.log({template})
}
main()

`getContractCode(name, addressMap)`

Returns Cadence template from file with name in _basepath_/contracts folder

Arguments

Name	Type	Optional	Description
`name`	string		name of the contract template
`addressMap`	AddressMap	✅	object to use for address mapping of existing deployed contracts

Returns

Type	Description
string	Cadence template code for specified contract

Usage

import path from "path"
import {init, emulator, getContractCode} from "@onflow/flow-js-testing"
const main = async () => {
  const basePath = path.resolve(__dirname, "../cadence")
  await init(basePath)
  await emulator.start()
  // Let's assume we need to import MessageContract
  await deployContractByName({name: "MessageContract"})
  const [MessageContract] = await getContractAddress("MessageContract")
  const addressMap = {MessageContract}
  const contractTemplate = await getContractCode("HelloWorld", {
    MessageContract,
  })
  console.log({contractTemplate})
  await emulator.stop()
}
main()

`getTransactionCode(name, addressMap)`

Returns Cadence template from file with name in _basepath_/transactions folder

Arguments

Name	Type	Optional	Description
`name`	string		name of the transaction template
`addressMap`	AddressMap	✅	object to use for address mapping of existing deployed contracts

Returns

Type	Description
string	Cadence template code for specified transaction

Usage

import path from "path"
import {init, emulator, getTransactionCode} from "@onflow/flow-js-testing"
const main = async () => {
  const basePath = path.resolve(__dirname, "../cadence")
  await init(basePath)
  await emulator.start()
  // Let's assume we need to import MessageContract
  await deployContractByName({name: "MessageContract"})
  const [MessageContract] = await getContractAddress("MessageContract")
  const addressMap = {MessageContract}
  const txTemplate = await getTransactionCode({
    name: "set-message",
    addressMap,
  })
  console.log({txTemplate})
  await emulator.stop()
}
main()

`getScriptCode(name, addressMap)`

Returns Cadence template from file with name in _basepath_/scripts folder

Arguments

Name	Type	Optional	Description
`name`	string		name of the script template
`addressMap`	AddressMap	✅	object to use for address mapping of existing deployed contracts

Returns

Type	Description
string	Cadence template code for specified script

Usage

import path from "path"
import {init, emulator, getScriptCode} from "@onflow/flow-js-testing"
const main = async () => {
  const basePath = path.resolve(__dirname, "../cadence")
  await init(basePath)
  await emulator.start()
  // Let's assume we need to import MessageContract
  await deployContractByName({name: "MessageContract"})
  const [MessageContract] = await getContractAddress("MessageContract")
  const addressMap = {MessageContract}
  const scriptTemplate = await getScriptCode({
    name: "get-message",
    addressMap,
  })
  console.log({scriptTemplate})
  await emulator.stop()
}
main()

Storage Inspection

getPaths

Retrieves information about the public, private, and storage paths for a given account.

Arguments

Name	Type	Description
`address`	`string`	The address or name of the account to retrieve the paths from.
`useSet` (optional)	`boolean`	Whether to return the paths as a Set or an array. Defaults to `true`.

Returns

An object containing the following properties:

Name	Type	Description
`publicPaths`	`Array<string>` or `Set<string>`	An array or Set of the public paths for the account, as strings.
`privatePaths`	`Array<string>` or `Set<string>`	An array or Set of the private paths for the account, as strings.
`storagePaths`	`Array<string>` or `Set<string>`	An array or Set of the storage paths for the account, as strings.

The useSet parameter determines whether the paths are returned as an array or Set. If useSet is true, the paths will be returned as a Set; otherwise, they will be returned as an array.

Usage

import path from "path"
import {init, emulator} from "@onflow/flow-js-testing"
import {getAccountAddress, getPaths} from "@onflow/flow-js-testing"
const main = async () => {
  const basePath = path.resolve(__dirname, "../cadence")
  await init(basePath)
  await emulator.start()
  // Get storage stats
  const Alice = await getAccountAddress("Alice")
  const paths = await getPaths(Alice)
  const {publicPaths, privatePaths, storagePaths} = paths
  // Output result to console
  console.log({Alice, paths})
  await emulator.stop()
}
main()

getPathsWithType

Retrieves public, private, and storage paths for a given account with extra information available on them

Arguments

Name	Type	Description
`address`	`string`	The address or name of the account to retrieve the paths from.

Returns

An object containing the following properties:

Name	Type	Description
`publicPaths`	`Object`	An object containing the public paths for the account, as keys and their types as values.
`privatePaths`	`Object`	An object containing the private paths for the account, as keys and their types as values.
`storagePaths`	`Object`	An object containing the storage paths for the account, as keys and their types as values.

The types of the paths are not strictly defined and may vary depending on the actual types used in the account.

Usage

import path from "path"
import {init, emulator} from "@onflow/flow-js-testing"
import {getPathsWithType} from "@onflow/flow-js-testing"
const main = async () => {
  const basePath = path.resolve(__dirname, "../cadence")
  await init(basePath)
  await emulator.start()
  const {publicPaths} = await getPathsWithType("Alice")
  const refTokenBalance = publicPaths.flowTokenBalance
  if (
    refTokenBalance.restrictionsList.has(
      "A.ee82856bf20e2aa6.FungibleToken.Balance"
    )
  ) {
    console.log("Found specific restriction")
  }
  if (refTokenBalance.haveRestrictions("FungibleToken.Balance")) {
    console.log("Found matching restriction")
  }
  await emulator.stop()
}
main()

getStorageValue

Arguments

Name	Type	Description
`account`	`string`	The address or name of the account to retrieve the storage value from.
`path`	`string`	The path of the storage value to retrieve.

Returns

Type	Description
`Promise<any>`	The value of the storage at the given path, or `null` if no value is found.

Usage

import path from "path"
import {init, emulator} from "@onflow/flow-js-testing"
import {sendTransaction, getStorageValue} from "@onflow/flow-js-testing"
const main = async () => {
  const basePath = path.resolve(__dirname, "../cadence")
  await init(basePath)
  await emulator.start()
  // Inplant some value into account
  await sendTransaction({
    code: `
        transaction{
          prepare(signer: AuthAccount){
            signer.save(42, to: /storage/answer)
          }
        }
      `,
    signers: [Alice],
  })
  const answer = await getStorageValue("Alice", "answer")
  console.log({answer})
  await emulator.stop()
}
main()

getStorageStats

Retrieves the storage statistics (used and capacity) for a given account.

Arguments

Name	Type	Description
`address`	`string`	The address or name of the account to check for storage statistics.
`convert` (optional)	`boolean`	Whether to convert the `used` and `capacity` values from strings to numbers. Defaults to `true`.

Returns

A Promise that resolves to an object containing the following properties:

Name	Type	Description
`used`	`number` or `string`	The amount of storage used by the account, in bytes.
`capacity`	`number` or `string`	The total storage capacity of the account, in bytes.

If convert is true, the used and capacity values will be converted from strings to numbers before being returned.

Usage

import path from "path"
import {init, emulator} from "@onflow/flow-js-testing"
import {getAccountAddress, getStorageStats} from "@onflow/flow-js-testing"
const main = async () => {
  const basePath = path.resolve(__dirname, "../cadence")
  await init(basePath)
  await emulator.start()
  // Get storage stats
  const Alice = await getAccountAddress("Alice")
  const {capacity, used} = await getStorageStats(Alice)
  // Output result to console
  console.log({Alice, capacity, used})
  await emulator.stop()
}
main()

Types

`AddressMap`

Object to use for address mapping of existing deployed contracts. Key shall be string and value shall be Address

Example

const addressMap = {
  Messanger: "0x01cf0e2f2f715450",
  Logger: "0x179b6b1cb6755e31",
}

`Interaction`

Interaction is a Promise or function returning a promise.

Example

const ix = async () => {
  return new Promise((resolve, reject) => {
    setTimeout(() => {
      resolve(1337)
    })
  }, 500)
}

`CadenceTransformer`

Function, which will get valid Cadence code, modify it and return valid Cadence code

Example

This transformer will look for occupancies of specific import statement and replace it with proper address, where it's deployed on Emulator

const replaceAddress = async code => {
  const modified = code.replace(
    /import\s+FungibleToken\s+from\s+0xFUNGIBLETOKEN/,
    "import FungibleToken from 0xee82856bf20e2aa6"
  )
  return modified
}

KeyObject

Key objects are used to specify signer keys when creating accounts.

Key	Required	Value Type	Description
`hashAlgorithm`	No	HashAlgorithm	Hashing algorithm to use for generating signatures to be signed by this key (default: `HashAlgorithm.SHA3_256`)
`privateKey`	Yes	string	Private key to use to generate the signature
`signatureAlgorithm`	No	SignatureAlgorithm	Signing algorithm used to sign transactions with this key (default: `SignatureAlgorithm.ECDSA_P256`)
`weight`	No	number	Weight of the key - see Flow Core Concepts for more information

PublicKey

Public keys are stored as Buffer objects which have been RLP encoded according to the Flow spec.

In order to generate this object using the Flow JS Testing library, use the pubFlowKey method exported by the library.

import {pubFlowKey} from "@onflow/flow-js-testing"
const pubKey = await pubFlowKey({
  privateKey: ...,
  hashAlgorithm: ...,
  signatureAlgorithm: ...,
  weight: ...
})

SignatureObject

Signature objects are used to represent a signature for a particular message as well as the account and keyId which signed for this message.

Key	Value Type	Description
`addr`	Address	the address of the account which this signature has been generated for
`keyId`	number	Address or SignerInfo object representing user to generate this signature for
`signature`	string	a hexidecimal-encoded string representation of the generated signature

SignerInfoObject

Signer Info objects are used to specify information about which signer and which key from this signer shall be used to sign a transaction.

Key	Required	Value Type	Description
`addr`	Yes	Address	The address of the signer's account
`hashAlgorithm`	No	HashAlgorithm	Hashing algorithm to use for generating the signature (default: `HashAlgorithm.SHA3_256`)
`keyId`	No	number	The index of the desired key to use from the signer's account (default: `0`)
`privateKey`	No	string	Private key to use to generate the signature (default: service account private key - this is the default PK for all accounts generated by Flow JS Testing Library, see: accounts)
`signatureAlgorithm`	No	SignatureAlgorithm	Signing algorithm used to generate the signature (default: `SignatureAlgorithm.ECDSA_P256`)

HashAlgorithm

Identifier	Value
SHA2_256	1
SHA3_256	3

Hash algorithms may be provided as either an enum (accessible via the HashAlgorithm object exported by Flow JS Testing, i.e. HashAlgorithm.SHA3_256) or as a string representation of their enum identifier (i.e. "SHA3_256")

SignatureAlgorithm

Identifier	Value
ECDSA_P256	2
ECDSA_secp256k1	3

Signing algorithms may be provided as either an enum (accessible via the SignatureAlgorithm object exported by Flow JS Testing, i.e. SignatureAlgorithm.ECDSA_P256) or as a string representation of their enum identifier (i.e. "ECDSA_P256")

Utilities

`isAddress(address)`

Returns true if the given string is a validly formatted account address (both "0x" prefixed and non-prefixed are valid)

Arguments

Name	Type	Optional	Description
`address`	string		string to test against the regex

Returns

Type	Description
boolean	Returns true if given string is a validly formatted account address.

Usage

import {isAddress} from "@onflow/flow-js-testing"
const badAddr = "0xqrtyff"
console.log(isAddress(badAddr)) // false
const goodAddrWithPrefix = "0xf8d6e0586b0a20c1"
console.log(isAddress(goodAddrWithPrefix)) // true
const goodAddrSansPrefix = "f8d6e0586b0a20c1"
console.log(isAddress(goodAddrSansPrefix)) // true

JS Testing API Reference

Accounts​

getAccountAddress​

Arguments​

Returns​

Usage​

createAccount({name, keys})​

Options​

Returns​

Contracts​

deployContractByName(props)​

Arguments​

Returns​

Usage​

deployContract(props)​

Arguments​

Returns​

Usage​

getContractAddress(name)​

Arguments​

Returns​

Usage​

Cryptography​

pubFlowKey(keyObject)​

Returns​

Usage​

signUserMessage(msgHex, signer, domainTag)​

Arguments​

Returns​

Usage​

verifyUserSigntatures(msgHex, signatures, domainTag)​

Arguments​

Returns​

Usage​

Emulator​

emulator.start(options)​

Arguments​

EmulatorOptions​

Returns​

Usage​

emulator.stop()​

Arguments​

Returns​

Usage​

emulator.setLogging(newState)​

Arguments​

Returns​

Usage​

FLOW Management​

getFlowBalance(address)​

Arguments​

Returns​

Usage​

mintFlow(recipient, amount)​

Arguments​

Returns​

Usage​

Init​

init( basePath, options)​

Arguments​

Options​

Returns​

Usage​

Environment​

getBlockOffset()​

Returns​

Usage​

setBlockOffset(offset)​

Arguments​

Returns​

Usage​

getTimestampOffset()​

Returns​

Usage​

setTimestampOffset(offset)​

Arguments​

Returns​

Usage​

Jest Helpers​

shallPass(ix)​

Accounts

`getAccountAddress`

Arguments

Returns

Usage

`createAccount({name, keys})`

Options

Returns

Contracts

`deployContractByName(props)`

Arguments

Returns

Usage

`deployContract(props)`

Arguments

Returns

Usage

`getContractAddress(name)`

Arguments

Returns

Usage

Cryptography

`pubFlowKey(keyObject)`

Returns

Usage

`signUserMessage(msgHex, signer, domainTag)`

Arguments

Returns

Usage

`verifyUserSigntatures(msgHex, signatures, domainTag)`

Arguments

Returns

Usage

Emulator

`emulator.start(options)`

Arguments

EmulatorOptions

Returns

Usage

`emulator.stop()`

Arguments

Returns

Usage

`emulator.setLogging(newState)`

Arguments

Returns

Usage

FLOW Management

`getFlowBalance(address)`

Arguments

Returns

Usage

`mintFlow(recipient, amount)`

Arguments

Returns

Usage

Init

init( basePath, options)

Arguments

Options

Returns

Usage

Environment

`getBlockOffset()`

Returns

Usage

`setBlockOffset(offset)`

Arguments

Returns

Usage

`getTimestampOffset()`

Returns

Usage

`setTimestampOffset(offset)`

Arguments

Returns

Usage

Jest Helpers

`shallPass(ix)`

Arguments