Testing Solidity/Ethereum smart contracts with Spock Framework

Please find full source in Github

I started this project after evaluating few tools for smart-contract development and not being particularly happy with any of them. It's based on the great Spock framework

Idea was to define the contract in the form of specification while developing it. Test themselves are directly connected to Ethereum test network, as mocking would make here even less sense than usual. Most of the problems that you wan't to discover occur from the network. If you are not familiar with spock or specification testing, please check my previous post on the subject

I just love docker in development as it helps to keep the dev environments uncluttered.

The compiler that compiles the solidity smart-contracts is run with docker. If your system does not support docker, you can install it manually and change the compileSolidity task in the build.gradle

This is a about smart-contract that allows 2 people sign a Deal with specific wordings. It is modeled according to this specification

The implementing contract is programmed as Solidity smart contract here

Rest of the project is really just dynamic glue code to bind the smart-contract and the specification together. Under the hood it uses web3j to generate Java wrappers from the Solidity. The glue should be generic and reusable to any smart-contract I might write in the future.

You need access to some Ethereum blockchain network. For me it did not make sense to run own node just for testing as it can take a lot of disk space and could be slow to start. So I used Infura which provides API that the standard client libraries know how to connect. From development perspective it functions as you would have your own node.

• Create Infura account (or other web3 compatible endpoint) and configure the address to purchaser.properties and supplier.properties

You need to pay GAS which is the cost of transaction when you create a smart-contract or execute any operations in the blockchain. This is paid in Ether.

To have ether, first you need a wallet. The wallet contains the address that is used as a key to pretty much everything. This is kind of your identifier in the blockchain. This project generates you 2 test wallets. You need 2 wallets, since we have two parties (Supplier and Purchaser) we need to test in our smart-contract.

To generate test wallets, execute gradle command gradle prepareFirstRun

In development you can use test networks, where you can obtain Ether more easily without having to actually pay. I used Rinkeby test network for which you can ask Ether from here

You should ask the Ether for your Supplier-wallet. To see the wallet ether-address after you generated it, execute gradle command gradle printSupplierWalletAddress

After you have Ether in your wallet, you can execute the previously mentioned prepareFirstRun again to transfer money from Supplier wallet to Purchaser wallet.

Gas price depends on the network and amount of Gas assigned to transaction may affect how fast it is processed. The test assigns a gas price by using a fraction of network indicated price. You can tune it on the SmartContract.groovy class if needed.

You can see transaction prices and other cool stats from the Rinkeby test network here

After the following preconditions are met (Machine has docker, properties-files contain the web3 endpoints and at least the Supplier wallet has Ether as described above)