Writing Truffle tests with async/await

The documentation and sample projects with Truffle use promise chaining to write the test code.  As someone from the C# world, coming into the JS world it was getting really confusing to keep track (as well as all the variables I’d have to declare outside of the promise chain to use later).

I did a bit of research and found a way to do async/await in Truffle. I have put up a small simple repo by taking the truffle init project sample, and then doing a straight 1:1 conversion of their promise chaining tests over to the async/await format to help illustrate the difference. I really like the async/await version, as it is cleaner to read and much more compact (as you can see in the before/after screenshots below).

You can find the repo at https://github.com/DavidBurela/TruffleAsyncTests

 

before – promise chaining https://github.com/DavidBurela/TruffleAsyncTests/blob/master/test/metacoin.js

image

 

after – with async/await https://github.com/DavidBurela/TruffleAsyncTests/blob/master/test/asyncmetacoin.js

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A shout out to Jim McDonald for pointing me to his GitHub repo where he had implemented async tests to get me started.

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Ethereum DevOps with VSTS – easier now with new Truffle installer + npx

Last year I blogged about my first attempt to wrap a DevOps flow around Ethereum development. Since then there have been improvements in the way that Truffle is deployed with npm, the npx command that comes with npm 5.3.0 onwards, VSTS now supporting hosted Linux build agents, but also my familiarity with Linux, npm & Truffle have increased. I have spent a few weeks in my spare time trying to vastly streamline and simplify getting a basic pipeline going that provides: compilation, testing, migrating of solidity contracts using Truffle.

The steps I outline below will work on any build system, such as Jenkins or Team city that can run bash commands. But I have shown VSTS as that is what I am most familiar with.

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Screenshot of the final result, with VTSTS showing Truffle test results for each build.

A video where I walk through the entire process end to end.

Example configured project

I have created a repository in GitHub where I have done the below steps. So if you want to just clone it and try it out on your own build server, that will make it easier for you

https://github.com/DavidBurela/truffledevops

1. Configure npm development packages for your Truffle project

Add Truffle, TestRPC, Mocha & Mocha JUnit plugin as DevDependencies in your packages.json. This will allow the build server to later install these packages and then execute Truffle commands.


# don't run npm init if your project already has a packages.json
npm init -y
npm install truffle ethereumjs-testrpc mocha mocha-junit-reporter --save-dev

2. Configure truffle.js

There are 2 main things that are being added here:

a) TestRPC provider as a new network, with the require at the top of the file to import it. This will allow Truffle to just spin up TestRPC just for the context of the command, and then get thrown away once the command finishes. Great for testing migrations, or running tests, and then throwing it all away.

b) Mocha test reporter definition. We leave it as “spec” so that it will display the results in the console window while developing locally. Later on the build server we can change the reporter to JUnit, and the output file is already specified here ready for that.


var TestRPC = require("ethereumjs-testrpc");

module.exports = {
networks: {
development: {
host: "localhost",
port: 8545,
network_id: "*" // Match any network id
},

// add a new network definition that will self host TestRPC
localtest: {
provider: TestRPC.provider(),
network_id:"*"
}
},

// add a section for mocha defaults
mocha: {
reporter: "spec",
reporterOptions: {
mochaFile: 'TEST-truffle.xml'
}
}
};

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3. Build server settings

This screenshot shows what the end result looks like. It can be summarised as: get the tests, install the npm packages, configure any environment variables, run the Truffle commands, and collect the test results.

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a) Get sources

Define where your code is sitting (e.g. VSTS, Github, Bitbucket, etc.)
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b) npm install

The default npm install task. Will look in packages.json and install our dev dependencies so later we can run Truffle, TestRPC, etc.
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c) Shell script – environment details and config

An inline script that spits out useful environment information to help debug if things go wrong.

It also importantly replaces the line in our truffle.js to change the test reporter to the console UI, to output the results into a .xml file in JUnit format


# output version details for debugging
node -v
npm -v
npx truffle version

# string replace the mocha reporter to junit output
sed -i -e 's/reporter: "spec"/reporter: "mocha-junit-reporter"/g' truffle.js

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d) Shell script – truffle commands

Inline script that executes the local version of Truffle with npx. I like have all 3 lines, so if something breaks we can see where it happened.


# check the contracts compile
npx truffle compile

# check migrations execute without issue
npx truffle migrate --network localtest

# run unit tests
npx truffle test --network localtest

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e) Publish test results

Default task. I have left the defaults
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