Testing Your Contracts

Truffle comes standard with an automated testing framework to make testing your contracts a breeze. This framework lets you write simple and manageable tests in two different ways:

  • In Javascript and TypeScript, for exercising your contracts from the outside world, just like your application.
  • In Solidity, for exercising your contracts in advanced, bare-to-the-metal scenarios.

Both styles of tests have their advantages and drawbacks. See the next two sections for a discussion of each one.

All test files should be located in the ./test directory. Truffle will only run test files with the following file extensions: .js, .ts, .es, .es6, and .jsx, and .sol. All other files are ignored.

To run all tests, simply run:

$ truffle test

Alternatively, you can specify a path to a specific file you want to run, e.g.,

$ truffle test ./path/to/test/file.js

Truffle provides a clean room environment when running your test files. When running your tests against Ganache or Truffle Develop, Truffle will use advanced snapshotting features to ensure your test files don't share state with each other. When running against other Ethereum clients like go-ethereum, Truffle will re-deploy all of your migrations at the beginning of every test file to ensure you have a fresh set of contracts to test against.

Both Ganache and Truffle Develop are significantly faster than other clients when running automated tests. Moreover, they contain special features which Truffle takes advantage of to speed up test runtime by almost 90%. As a general workflow, we recommend you use Ganache or Truffle Develop during normal development and testing, and then run your tests once against go-ethereum or another official Ethereum client when you're gearing up to deploy to live or production networks.

You can obtain Solidity stack traces for failed transactions with truffle test --stacktrace. This will produce stack traces for transactions and deployments made via Truffle Contract during your tests should one of them revert and thereby causes your test to fail. This option is still experimental, and stack traces are not currently supported for calls or gas estimates. Moreover, while it is turned on, PromiEvent functionality of Truffle Contract (as opposed to Promise functionality) may not work.

There is also the option truffle test --stacktrace-extra. This will turn on stack traces and will additionally compile contracts in Solidity's debug mode for additional revert messages. This debug mode was only introduced in Solidity 0.6.3 so it will have no effect on earlier versions of Solidity. Using debug mode may cause problems on larger contracts.