Installation

Running Live Contracts requires using the LTO Network workflow node.

In these tutorials, we're always using the developer build of the workflow node, which is available as a Docker container.

curl "https://raw.githubusercontent.com/ltonetwork/lto-workflow-node/docker-compose.yml" -o docker-compose.yml
docker-compose up

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JSON screenshot

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To check that the node is correctly up visit https://localhost:3000. You'll see a JSON response containing information about the LTO services.

JSON screenshot

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Project directory structure

mkdir -p livecontracts-tutorial
cd livecontracts-tutorial

Creating a scenario

A Live Contract must contain one or more scenarios that describe the process(es) we're automating. We can write a scenario in either JSON or YAML.

$schema: "https://specs.livecontracts.io/v0.2.0/scenario/schema.json#"
title: The basics

{
    "$schema": "https://specs.livecontracts.io/v0.2.0/scenario/schema.json#",
    "title": "The basics"
}

Defining actors

Actors are organizations or individuals that play a role in the process. The scenario needs to define which actors (may) exist.

$schema: "https://specs.livecontracts.io/v0.2.0/scenario/schema.json#"
title: The basics
​
actors:
  initiator:
    title: Initiator

{
    "$schema": "https://specs.livecontracts.io/v0.2.0/scenario/schema.json#",
    "title": "The basics",
    "actors": {
        "initiator": {
            "title": "Initiator"
        }
    }
}

We've defined a single actor for the process; the initiator. Normally a process contains 2 or more actors.

Defining actions

All actions that any actor can perform within the process must be defined at forehand in the scenario.

$schema: "https://specs.livecontracts.io/v0.2.0/scenario/schema.json#"
title: My first Live Contract
​
actors:
  initiator:
    title: Initiator
    
actions:
  complete:
    title: Complete the process
    actor: initiator

{
    "$schema": "https://specs.livecontracts.io/v0.2.0/scenario/schema.json#",
    "title": "The basics",
    "actors": {
        "initiator": {
            "title": "Initiator"
        }
    },
    "actions": {
        "complete": {
            "title": "Complete the process",
            "actor": "initiator"
        }
    }
}

The complete action can be performed by the initiator actor. The intend of this action is to complete the process. However, that transition needs to be defined in the state.

The initial state

When a process is started, it's in the initial state. From this state it can transition to other states, until the process is completed.

$schema: "https://specs.livecontracts.io/v0.2.0/scenario/schema.json#"
title: My first Live Contract
​
actors:
  initiator:
    title: Initiator
    
actions:
  complete:
    title: Complete the process
    actor: initiator
    
states:
  initial:
    action: complete
    transition: :success

{
    "$schema": "https://specs.livecontracts.io/v0.2.0/scenario/schema.json#",
    "title": "Basic user",
    "actors": {
        "initiator": {
            "title": "Initiator"
        }
    },
    "actions": {
        "complete": {
            "title": "Complete the process",
            "actor": "initiator"
        }
    },
    "states": {
        "initial": {
            "action": "complete",
            "transition": ":success"
        }
    }
}

While in the initial state, only the complete action can be performed. Once the action is performed, the process will transition to the :success end state, meaning the process has been completed successfully.

Running a test

To ensure the Live Contract behaves as expected, we need to create and run tests. Tests must be defined using the Gherkin syntax. The Live Contracts test suite that comes with the full node, defines the steps that can be used in the test.

main.feature
Feature: Run a simple process that is completed in one step
​
  Background:
    Given a chain is created by "Joe"
    Given "Joe" creates the "main" process using the "basic" scenario
    And   "Joe" is the "initiator" actor of the "main" process
​
  Scenario:
    When "Joe" runs the "complete" action of the "main" process
    Then the "main" process is completed

We have a single identity named "Joe". The name is arbitrary but used to keep the identities apart.

Joe initializes the Live Contract by creating a new chain and using our basic scenario. The process name "main" is also arbitrary and used to reference a specific process. It's possible to run multiple processes for a Live Contract, but in our case, only a single process exists.

We need to specify which role Joe is going to have in the process. In this case, he's the initiator of the process.

In the Scenario section (this is unrelated to the workflow scenario), we state that will Joe performs the complete action. As defined in our workflow scenario, the process should transition from initial to :success, which means the process has been completed successfully.

Running the Live contract tester

lctest is a command-line tool to test workflows described in a Live Contract. It can be run from the ltonetwork/letsflow-test docker container.

docker run ltonetwork/letsflow-test basic

The test should succeed, giving the following output:

Congratulations!

You've successfully created and tested your first Live Contract.

Continue

For more workflow tutorials visit LetsFlow.