Ethereum by Bruno Skvorc

Author:Bruno Skvorc [Various]
Language: eng
Format: epub
Publisher: SitePoint
Published: 2017-08-08T23:00:00+00:00

JavaScript Testing

Truffle enables us to use JavaScript for testing, leveraging the Mocha testing framework. This enables you to write more complex tests and get more functionality out of your testing framework.

Okay, let’s write the test. First, in the test folder, create a file and call it hashmarket.js.

The first thing we need to do, is get the reference to our contract in JavaScript. For that, we’ll use Truffle’s artifacts.require(...) function:

var HashMarket = artifacts.require("./HashMarket.sol");

Now that we have the reference to the contract, let’s start writing tests. To start, we’ll use the contract function provided to us:

contract("HashMarket", function(accounts) { });

This creates a test suite for our contract. Now for testing, we use Mocha it syntax:

contract("HashMarket", function(accounts) { it("should add a new product", function() { }); });

This describes the test we’ll write and presents a message for us to know the purpose of the test. Now let’s write the test itself. At the end, the hashmarket.js file should look like the following. The reasoning is explained in the comments of the source code:

var HashMarket = artifacts.require("./HashMarket.sol"); contract("HashMarket", function(accounts) { it("should add a new product", function() { // Set the names of test data var itemName = "TestItem"; var itemPrice = 1000; var itemSeller = accounts[0]; // Since all of our testing functions are async, we store the // contract instance at a higher level to enable access from // all functions var hashMarketContract; // Item ID will be provided asynchronously so we extract it var itemID; return HashMarket.deployed().then(function(instance) { // set contract instance into a variable hashMarketContract = instance; // Subscribe to a Solidity event instance.ItemAdded({}).watch((error, result) => { if (error) { console.log(error); } // Once the event is triggered, store the result in the // external variable itemID = result.args.itemID; }); // Call the addNewItem function and return the promise return instance.addNewItem(itemName, itemPrice, {from: itemSeller}); }).then(function() { // This function is triggered after the addNewItem call transaction // has been mined. Now call the getItem function with the itemID // we received from the event return hashMarketContract.getItem.call(itemID); }).then(function(result) { // The result of getItem is a tuple, we can deconstruct it // to variables like this var [name, price, seller, status] = result; // Start testing. Use web3.toAscii() to convert the result of // the smart contract from Solidity bytecode to ASCII. After that // use the .replace() to pad the excess bytes from bytes32 assert.equal(itemName, web3.toAscii(name).replace(/\u0000/g, ''), "Name wasn't properly added"); // Use assert.equal() to check all the variables assert.equal(itemPrice, price, "Price wasn't properly added"); assert.equal(itemSeller, seller, "Seller wasn't properly added"); assert.equal(status, 0, "Status wasn't properly added"); }); }); });

Run truffle test and you should get something like this:

TestHashMarket ✓ testAddingNewProduct (109ms) Contract: HashMarket ✓ should add a new product (64ms) 2 passing (876ms)

Your test has passed and you can be confident about not having regression bugs.

For homework, write tests for all other functions in the contract.

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