Koinos-Mock-VM is a NodeJS application/package that allows you to run WASM Koinos smart contracts without deploying the contracts to the Koinos blockchain. It is a tool that you can leverage to build unit tests for your smart contracts.

You need to install NodeJS v16 or higher download

# with npm
npm install -g @roamin/koinos-mock-vm

# with yarn
yarn global add @roamin/koinos-mock-vm

koinos-mock-vm leverages the Koinos system calls to enable a wasm contract to interact with the mock vm, which means that any Koinos wasm contract can use it out of the box.

The put_object system call is used to insert mock data in the database powering the mock vm. When calling a system call, like get_entry_point, the mock vm will pull the mock data that was initially set in the database. The metadata system space is used to store the mock data. (space zone = "", space id = 0, system = true)

List of keys used to store the mock data:

• entry_point:
  • object of type koinos.chain.value_type with the int32_value property set with the entry point
  • used by the system call get_entry_point
• contract_arguments:
  • object of type bytes set with the contract arguments
  • used by the system call get_contract_argument
• contract_result:
  • object of type bytes set with the contract result
  • used by the system call set_contract_result
• contract_id:
  • object of type bytes set with the contract id
  • usde by the system call get_contract_id
• head_info:
  • object of type koinos.chain.head_info set with the head info
  • used by the system call get_head_info
• caller:
  • object of type koinos.chain.caller_data set with the caller data info
  • used by the system call get_caller
• last_irreversible_block:
  • object of type koinos.chain.value_type with the uint64_value property set with the last irreversible block height
  • used by the system call get_last_irreversible_block
• transaction:
  • object of type koinos.protocol.transaction set with the transaction info
  • used by the system calls get_transaction and get_transaction_field
• operation:
  • object of type koinos.protocol.operation set with the operation info
  • used by the system calls get_operation
• block:
  • object of type koinos.protocol.block set with the block info
  • used by the system calls get_block and get_block_field
• authority:
  • object of type koinos.chain.list_type. Each koinos.chain.value_type elements represent an authorization:
    • int32_value: value of the koinos.chain.authorization_type
    • bytes_value: bytes of the account address
    • bool_value: "autorized" boolean
  • used by the system call require_authority:
    • will use the require_authority arguments (type and account) to lookup the autorization in the previously set koinos.chain.list_type
• call_contract_results:
  • object of type koinos.chain.list_type. Each koinos.chain.value_type elements represent a contract call result:
    • bytes_value: bytes of the contract call result
  • used by the system call call_contract:
    • will use the previously set koinos.chain.list_type to return a call result. The call contract results are FIFO meaning that the first call_contract will use the first element you set in the list, the second call the second element in the list, etc...
• logs:
  • object of type koinos.chain.list_type. Each koinos.chain.value_type has its string_value set with a log
  • used by the system call log
• events:
  • object of type koinos.chain.list_type. Each koinos.chain.value_type has its bytes_value set with a koinos.protocol.event_data object
  • used by the system call event
• exit_code:
  • object of type koinos.chain.exit_contract_arguments
  • used by the system call exit_contract

The following keys are additional commands that allow you to interact with the mock vm's database:

• reset:
  • whatever object as argument
  • will reset the database
• rollback_transaction:
  • whatever object as argument
  • will restore the backup made in the previous commit_transaction
• commit_transaction:
  • whatever object as argument
  • will save a backup of the actual state of the database (useful when trying to build unit tests around transaction reversions)

Example for setting the contract id in an AssemblyScript Koinos smart contract:

const metadataSpace = new chain.object_space();
metadataSpace.system = true;
metadataSpace.id = 0;

System.putBytes(metadataSpace, 'contract_id', Base58.decode('1DQzuCcTKacbs9GGScRTU1Hc8BsyARTPqe'));

const contractId = System.getContractId();
System.log('contractId: ' + Base58.encode(contractId));
// will print contractId: 1DQzuCcTKacbs9GGScRTU1Hc8BsyARTPqe

You can execute multiple smart contracts in one run, they will be executed in the order they appear in the command parameters. The koinos-mock-vm database will be shared between each execution allowing you to build complex executions cases that involve several contracts.

koinos-mock-vm <path to contract wasm 1> <path to contract wasm 2> ... <path to contract wasm n>

See index.js file in the bin folder.

koinos-mock-vm contract.wasm

[Starting VM] 1 contracts to execute
[Execution started] contract.wasm
[Log] entryPoint: 3282800625
[Log] contract_arguments: myArgs
[Log] contract_id: 1DQzuCcTKacbs9GGScRTU1Hc8BsyARTPqe
[Execution completed] in 16.232577ms contract.wasm
[Stopping VM] exit code 0