specron – a lightweight, open source and magic-free framework for testing Solidity smart contracts.
import { Spec } from ' @specron/spec ' ; const spec = new Spec (); spec . before ( 'returns boolean' , async ( ctx ) => { const main = await ctx . deploy ({ src: './build/main.json' , contract: 'Main' , }); ctx . true ( await main . methods . works (). call ()); }); export default spec ;
~/myProject $ npm test Sources ./src/contracts/main.sol Contracts ./src/contracts/main.sol: Main 1 contracts 1 sources src/tests/main.test.ts returns boolean 1 passing ~/myProject $

Specron Framework

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Specron is a lightweight, open source, magic-free framework for testing smart contracts written in Solidity. The testing suite is built on top of the Hayspec framework thus using TypeScript is supported.

Specron provides development environment for the Ethereum blockchain and includes useful tools which enable developers to easily write tests for smart contracts.

The source code is available on GitHub where you can also find our issue tracker.


Start by installing the Specron command-line tool.

$ npm install -g @specron/cli web3 solc

Specron depends on the latest web3 and solc packages, so make sure you have them globally installed. Specron also uses promises thus you need to use Promise polyfill when promises are not supported.

Getting started

Specron automates the testing process of your Solidity code. It doesn’t require you to install certain applications in order to get started.

The Specron interface is designed to fully support the power of TypeScript when writing tests. It is magic-free which means you have a complete control and visibility of what the code does and how tests are executed. The testing flow should look familiar to any JavaScript or TypeScript developer.

Project initialization

Start by creating a new project folder.

$ mkdir myproject
$ cd myproject

Initialize the project and install the dependencies.

$ specron init
$ npm install

Run tests to verify everything works as expected.

$ npm test

Writing tests

The core test functionality is provided by the @specron/spec module which is automatically attached to your project at initialization. Here we explain some of the main framework features but please explore the source code to find out all the possibilities.

Initializing specs

The framework provides a Spec class which holds basically the whole testing power. You start your test by creating an instance of that class.

import { Spec } from '@specron/spec';

const spec = new Spec();

Testing features

The Spec instance provides methods that you can use when writing tests. Most of the time you will use the test method which performs the test you write.

spec.test('is true', async (ctx) => { // promise | function

There is also the skip method which prevents a test to be performed, and the only method which includes itself into the test process but excludes all other tests.

Nested specs

Tests can be nested using the spec method.

const colors = new Spec();
spec.spec('colors', colors);

Using callbacks

The framework provides before and after methods which are execute at the beginning and at the end of the spec case.

spec.before((stage) => {
  // execute before all tests
spec.after((stage) => {
  // execute after all tests

These methods have access to the stage of the spec instance. The stage is global to the whole spec stack which means that all settings are always preserved.

There are also the beforeEach and afterEach methods which are triggered before and after each test. These methods have access to the context and stage of the spec. The context represents a copy of a stage and is preserved between beforeEach, test and afterEach methods. This allows for testing atomic tests where a fresh context is always created for each test.

spec.beforeEach((context, stage) => {
  // execute before all tests
spec.afterEach((context, stage) => {
  // execute after all tests

Callback functions can be called multiple times and the execution will happen in a defined sequence.

Shared data

The context and the stage both provide a way to set and get values with proper TypeScript types.

interface Data {
  id: number;
  name: string;

const spec = new Spec<Data>();

spec.beforeEach((ctx) => {
  ctx.set('id', 100);
  ctx.set('name', 'John');

spec.test('is John with id=100', (ctx) => {
  const id = ctx.get('id');
  const name = ctx.get('name');
  ctx.is(id, 100);
  ctx.is(name, 'John');

Values set inside the before and after blocks are available to all spec methods. Values set in the beforeEach and afterEach blocks are available only on the context stack of each test.

Contract deployment

Stage and context both provide a series of different helper methods.

A very important method is the deploy() method which deploys a contract to a local blockchain process in the background and returns a contract instance.

const { instance, receipt } = await ctx.deploy({
  src: './contracts.json',
  contract: 'Main',

Using CLI

The @specron/cli module is automatically installed when you initialize the project. You can interact with the utility using the npx specron command in your terminal.

To get a list of available features use the --help flag.

$ npx specron --help

Running tests

Every test file must export the spec instance for the CLI to be able to detect the test.

export default spec;

Run the specron test command to run tests. Customize the files search by using the --match flag.

$ npx specron test --match ./**/*.test.*

TypeScript support

Install the ts-node NPM package then use the --require flag to enable TypeScript support.

specron --require ts-node/register

Project configuration

Specron configuration options can be saved inside the package.json file under the the specron key.

  "specron": {
    "compiler": {
      "build": "./build",
      "match": [
      "severities": [
      "evmVersion": "byzantium"
    "flattener": {
      "build": "./build",
      "match": [
      "severities": [
    "sandbox": {
      "port": 8545,
      "host": "localhost"
    "test": {
      "server": true,
      "port": 8545,
      "host": "localhost",
      "match": [
    "require": [

Note that these options can be overriden by providing CLI arguments.

Using continuous integration

For a full example of a Solidity contract repository including continuous integration using Travis and Specron, see https://github.com/xpepermint/specron-example.


Package Description Version
@specron/cli Command-line interface. NPM Version
@specron/compiler Smart contracts compiler. NPM Version
@specron/flattener Smart contracts flattener. NPM Version
@specron/init Project structure initializer. NPM Version
@specron/sandbox Ethereum sandbox server. NPM Version
@specron/spec Core test suite. NPM Version


See CONTRIBUTING.md for how to help out.


See LICENSE for details.