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sUnit

Disclaimer: Running and using this library is difficult. It is alpha software, and it uses an alpha client to test code written in a language (Solidity) that is still under development. The library should be considered experimental.

Introduction

sUnit (solUnit) is a unit testing framework for Solidity contracts. It runs unit tests against javascript Ethereum.

The name of this library is solUnit, because sUnit is the Smalltalk unit testing framework, but because there is no chance of confusion (nobody has unit-tested Smalltalk since the 90s) those aliases are sometimes used instead. The node package is called s-unit, but the github repo is sol-unit.

NOTE: Static coverage analysis (parsing syntax trees) has been removed in 0.3 to be replaced by runtime analysis later. I plan on adding other analytics tools as well, with the new VM and all...

Installing

Only tested on linux (Ubuntu 14.04, 14.10, 15.04).

npm install s-unit

Use the --global flag to get the sunit command-line version into PATH.

Usage

The executable name is sunit. If you install it globally you should get it on your path. Try $ sunit -V and it should print out the version.

To see all the options:

$ sunit --help

  Usage: sunit [options] <test ...>

  Options:

    -h, --help           output usage information
    -V, --version        output the version number
    -m, --debugMessages  Print debugging information. [default=false]
    -d, --dir <dir>      Directory in which to do the tests. [default=current directory]

Example: $ sunit ArrayTest CoinTest will look for those tests in the current directory, or simply typing sunit in a folder with tests in it will run all tests in the folder.

Test names are the test contract names. They should always end in Test (no extension).

The library can be run from javascript as well:

var SUnit = require('s-unit');

var tests = new SUnit();

// Need to set event listeners up manually. 
  
sUnit.on('suiteStarted', function(error, tests){console.log(tests)});
sUnit.on('contractStarted', someFunc);
// ...

tests.start(['ArrayTest', 'CoinTest'], 'rootdir');

Event-listeners are documented in the library structure section near the bottom of this document.

Motivation

Unit testing Solidity using Solidity has the same benefits as unit testing anything else. It is perfect for testing input validation and other things, to complement formal analysis etc.

Calling contracts from javascript (web3.js in a web-page or alethzero) is integration testing, not unit testing. A good project should in my opinion have both kinds of tests.

Writing tests

The easiest way to start writing unit-testing contracts is to look at the examples in contracts/src.

Test format

The rules for a unit testing contract right now (0.3.x) are these:

Test-contracts must use the same name as the test target but end with Test. If you want to test a contract named Arrays, name the test-contract ArraysTest. If you want to test a contract named Coin, name the test-contract CoinTest, and so on.
Test function names must start with test, e.g. function testAddTwoInts(), and they must be public. There is no limit on the number of test-functions that can be in each test-contract.
The test-contract may use a test event: event TestEvent(bool indexed result, string message);. The recommended way of doing unit tests is to have the test-contract extend Asserter, by importing Asserter.sol (comes with the library). Its assertion methods has a proper test event already set up which will fire automatically when an assertion is made. There is no limit on the number of assertions in a test method.

NOTE: If none of the existing assertions would fit, extend the Asserter.sol contract or calculate the result in the test-function and use assertTrue or assertFalse.

A test passes if no assertion fails (i.e. result is true in every test event). If no assertions are made, the test will pass automatically. If at least one assertion fails, the test will not pass.

Example of a simple storage value test

import "./assertions/Asserter.sol";

contract Demo {
    
    uint _x = 0;
    
    function setX(uint x){
        _x = x;
    }
    
    function getX() constant returns (uint x){
        return _x;
    }
}

// Test contract named DemoTest as per (1).
contract DemoTest is Asserter {

    uint constant TEST_VAL = 55;
    
    // Test method starts with 'test' and will thus be recognized (2).
    function testSetX(){
        Demo demo = new Demo();
        assertAddressNotZero(address(demo), "Failed to deploy demo contract");
        demo.setX(TEST_VAL);
        var x = demo.getX();
        // Use assert method from Asserter contract (3). It will automatically fire off a test event.
        assertUintsEqual(x, TEST_VAL, "Values are not equal");
    }
    
}

There is plenty more in the contracts/src folder. All test contracts looks pretty much the same - a target contract and a few methods that begin with 'test' and has assertions in them.

Build constraints

The .bin and .abi files for the test contracts must be available in the working directory.

Example

I want to unit test a contract named Bank. I create BankTest, compile the sources, and make sure the following files are created: BankTest.bin, BankTest.abi.

To make sure I get all of this, I compile with: solc --bin --abi -o . BankTest.sol. They will end up in the same folder as the sources in this case.

TestEvent and assertions

TestEvent is what the framework listens too. It will run test functions and then listen to TestEvent data from the contract in question.

event TestEvent(bool indexed result, string message);

The result param is true if the assertion succeeded, otherwise it's false.

The message param is used to log a message. This is normally used if the assertion fails.

If the contract extends Asserter, it will inherit TestEvent, and can also use the assert methods which will automatically trigger the test event. Otherwise you can just roll your own.

Example of a bare-bones test contract

contract Something {
    
    int _something;
    
    function setSomething(int something){
        _something = something;
    }
    
    function something() constant returns (int something){
        return _something;
    }
}

contract SomethingTest {

    event TestEvent(bool indexed result, string message);
    
    function testSomething(){
        Something testee = new Something();
        int someValue = 5; 
        testee.setSomething(someValue);
        var intOrSomeSuch = testee.something();
        var result = (intOrSomeSuch == someValue);
        if(result){
            TestEvent(true, "");
        } else {
            TestEvent(false, "Something is wrong.");
        }
    }

}

Examples

The contracts folder comes with a number of different examples.

Tests

mocha or npm test.

It is also possible to run the executable from the ./contracts/build folder, either sunit if it is installed globally, or ../../../bin/sunit.js. NOTE: One test always fails, just to show how it looks.

Library structure

The framework uses Solidity events (log events) to do the tests. It uses the afore-mentioned Solidity TestEvent to get confirmation from contract test-methods.

The SUnit class is where everything is coordinated. It deploys the test contracts and publish the results via events. It implements nodes EventEmitter. It forwards some of these events from dependencies like the TestRunner, which is also an emitter.

The TestRunner takes a test contract, finds all test methods in it and run those. It also sets up a listener for solidity events and uses those events to determine if a test was successful or not. It is normally instantiated and managed by a SUnit object.

In the diagram, the executable gathers the tests and set things up, then SUnit deal with the contract execution part.

Presentation of test data is not part of the diagram. The core SUnit library does not present - it only passes data through events. The way presentation works in the command-line tool is it listens to all SUnit events and prints the reported data using a special test-logger.

Events

SUnit extends Node.js' EventEmitter.

The events you may listen to are these:

Suite started

id: 'suiteStarted' - The suite has started.

callback params: error, tests - array of test names. Keep in mind these may not be the same as you entered, because some may not have existed or you could have skipped the names so that it found all tests in the directory. This is the list of tests (test contracts) that was actually found.