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0.0.17 • Public • Published


💡 Inspired by dapptools's ds-test.

⚠️ Requires hardhat-deploy as a peer dependency.


Tests suites are solidity contracts, tests are solidity functions.



$ npm install @mangrovedao/hardhat-test-solidity




// Adds Test library to the context
import Test from "@mangrovedao/hardhat-test-solidity/test.sol";

// `_Test` suffix means it is a test contract
contract MyContract_Test {

  receive() external payable {} // necessary to receive eth from test runner

  // `_test` suffix means it is a test function
  function addition_test() public {
    // Logging will be interpreted by hardhat-test-solidity
    Test.eq(4,2+2,"oh no");

  // Will not be interpreted as a test function
  function prepare() public {}


$ npx hardhat test-solidity MyContract

How to structure test contract

  • All contracts with suffix _Test are test contracts.
  • All public functions with suffix _test are test functions.
  • All public functions with suffix _beforeAll setup the state before other tests.
  • If you have the functions fn_test and fn_before, fn_before will run, then fn_test, without state revert.


  • You must make a receive function so your test contracts get ethers.
  • State is reverted between tests
  • Functions are sorted alphabetically before they are added to test suite
  • You probably want a MyContract_Test for every MyContract.
  • Having multiple _beforeAll functions rather than setting things up in the constructor means you can split setup into multiple transactions to go around gas limits.

How to test for stuff

  • Test.check(bool success,string memory message) succeeds if success is true.
  • Test.eq(actual,expected,message) for testing bytes32, bool, string, uint, address equality.
  • Test.eq0(actual,expected,message) for testing bytes equality.
  • Test.less(uint a, uint b,message) succeeds if a < b.
  • Test.more(uint a, uint b,message) succeeds if a > b.
  • Test.fail(message) to always fail.
  • Test.succeed() to always succeed.

How to test for event emission

Suppose you want to make sure that contract Market emits the Trade event.

import "@mangrovedao/hardhat-test-solidity/test.sol";
contract My_Test {
  receive() external payable {} // necessary to receive eth from test runner

  Market amm;

  function _beforeAll() {
    amm = new Market()

  function first_test() {

    emit Market.Trade();

So: you emit an event (with any arguments you like), and the plugin will check that amm has already emitted the exact same event.


  • For a given address, the order of events matters. Between addresses it does not.
  • Events are checked after their emission. So do all your test, and at the end test for events.
  • If you want to normally emit events from a test after you already called Test.expectFrom(address), call Test.stopExpecting();

How to use the command line

npx hardhat test-solidity [contract names without _Test] [--prefix function_prefix]

Add --details for more detailed logging, including logs generated by the logFormatters plugin option (see below).

For more CLI options look at

npx hardhat test-solidity --help


If you want to only run the test breath_is_fire_test in the testing contract Dragon_Test, and you have 10 testing contracts, run

test-solidity Dragon --prefix breath_is_fire

rather than just

test-solidity --prefix breath_is_fire

so you don't waste time deploying all the other test suite contracts.

How to log

To get nicely-formatted logs, use the Display library. There are

  • Display.log(uint|string)
  • Display.log(uint|string,uint|string)
  • Display.log(uint|string,uint|string,uint|string)
  • Display.logBalances(address[1] memory tokens, address a0)
  • Display.logBalances(address[1] memory tokens, address a0, address a1)
  • Display.logBalances(address[1] memory tokens, address a0, address a1, address a2)
  • Display.logBalances(address[2] memory tokens, address a0)
  • Display.logBalances(address[2] memory tokens, address a0, address a1)
  • Display.logBalances(address[2] memory tokens, address a0, address a1, address a2)

How to register addresses

To get pretty-printing of addresses, in your test setup do

import {Display as D} from "@mangrovedao/hardhat-test-solidity/test.sol";
D.register(address addr, string memory name)

then when using --show-events and wherever addresses are used, name will be shown instead of addr.

How to configure the plugin


  testSolidity: { // default values as follows:
    timeout: 300_000 /* test suite timeout in ms */,
    logFormatters: (hre,formatArg) => { return {}; } /* format logs */
    testers: (hre,formatArg,assert) => { return {}; } /* format logs */

Custom log formatters

logFormatters(hre,formatArg):object is a function that takes the hre hardhat runtime environment and a formatArg(arg,type?):string utility function. arg is dynamically tested and type is an optional type hint (it can be uint, address, or an array of type hints) to help formatting.

logFormatters should return an object where keys are event names and values are formatting functions that should directly log to console and have type:



See src/logFormatters.js for examples.

Custom testers/assertions

testers(hre,formatArg,assert/*assert library*/) takes the hre, formatArg, and the chai assert object, and returns an object where keys are test event names and values are of the form :

  trigger({success,message,actual,expected}) : void

You should create the corresponding events in your tests so that they can be interpreted by your functions.


See src/testers.js for examples.


This plugin uses the debug package. To debug this plugin only do:

DEBUG='hardhat:test-solidity:*' npx hardhat test-solidity [args]

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