"Echidna" is a fuzzing / property-based testing tool for Ethereum Smart Contracts. With Echidna you can generate random input data according to your Smart Contract ABIs.
This is very useful for automated tests as you don't have to come up with the assertions but Enchida does. Once a problem is found, Echidna lets you further shrink down the input domain to find an exact way to reproduce the issue.
Protip: Use <a href="https://github.com/crytic/etheno">Etheno</a> to simplify the setup of Echidna in large multi-contract projects.

Tool to fuzz / property test Ethereum Virtual Machine (EVM) Smart Contracts.

Echidna

The "Etheno" project helps you integrate analysis tools such as Manticore and Echidna in large, multi-contract projects.
Its features include:
<ul>
<li>JSON RPC Multiplexing</li>
<li>Analysis Tool Wrapping</li>
<li>Test Framework Integration</li>
</ul>

Tool to simplify Ethereum Virtual Machine (EVM) security analysis and testing.

Etheno

The "Vertigo" project is a CLI tool to run mutation tests against EVM-based Smart Contracts written via development frameworks such as Hardhat or Truffle.
Protip: If you're new to mutation testing you might want to read through the author's introductory <a href="https://medium.com/swlh/introduction-into-mutation-testing-d6512dc702b0">blog post</a>.

Mutation testing framework for Ethereum Virtual Machine (EVM) Smart Contracts.

Vertigo

Brownie is a development and testing framework for Smart Contracts targeting the Ethereum Virtual Machine. It has full support for languages like Solidity and Vyper, powerful debugging tools as well as a package manager.
Protip: Brownie also ships with a built-in console you can use to quickly interact with and iterate on your project.

Development and testing framework for Smart Contracts targeting the Ethereum Virtual Machine (EVM).

Brownie

Using cliquebait you can spin up an easy to use single-node Proof-of-Authority Blockchain via Geth running in Docker. Cliquebait also automatically generates accounts with ETH you can unlock to easily deploy and test your Smart Contracts.
Cliquebait's main goals is to simplify integration- and acceptance testing of dApps by offering an ephemeral testing environment that closely resembles a real Blockchain network.

Docker container that spins up a PoA Blockchain for testing.

Cliquebait

eth-gas-reporter is a Mocha reporter for Ethereum test suites which provides you insights into your Smart Contract's gas usage. Using it you can see a breakdown of gas usage per unit test, metrics for method calls and deployments as well as costs of deploying and using your Smart Contract system.
Protip: If you're using Truffle or Hardhat you can find more information about official support and proper setup in the <a href="https://github.com/cgewecke/eth-gas-reporter/blob/master/README.md">README</a>.

Generate gas usage reports for your Smart Contracts.

Eth Gas Reporter

The eth-tester project is a tool suite which provides high-level abstractions to test Ethereum dApps. It's written in Python and can be used programmatically as a project dependency or interactively via the CLI.
Ethereum Tester's implementation focuses on modularity which makes it possible to use different backends for different test scenarios.

Tool suite to test Ethereum Virtual Machine (EVM) based applications.

Ethereum Tester

Not every project you're working necessarily uses the same Solidity compiler. With solc-select you can easily switch between different Solidity compiler versions without breaking your existing development environment

Easily switch between different Solidity compiler versions.

Solc Select

Whenever you're testing code you want to ensure that you cover all critical code paths. Test / Code coverage tools help you in figuring that out.
The solidity-coverage project is a code coverage tool for Smart Contracts written in Solidity. Simply install the package and add it to your Truffle / Hardhat config to get detailed code coverage reports every time you run your tests.

Code coverage reports for Smart Contracts written in Solidity.

Solidity Coverage

"Waffle" is the most advanced Smart Contract testing framework. It integrates nicely with development frameworks such as Ganache or Hardhat, is minimalistic with only a few dependencies, has a nice and easy to remember syntax and is fast in both, development- and execution time.
Protip: You should definitely spend some time to read through their <a href="https://ethereum-waffle.readthedocs.io/en/latest/">documentation</a>. The <a href="https://ethereum-waffle.readthedocs.io/en/latest/matchers.html">Chai matchers docs</a> in particular explain how you can make use of their custom matchers to e.g. check for BigNumbers or events emitted by your contracts.

Testing framework for Smart Contracts targeting the Ethereum Virtual Machine (EVM).

Waffle

"OpenZeppelin Test Helpers" is an assertion library which makes it easier to test EVM-based Smart Contracts. Using it you can easily check if reverts happen for the right reason, events are emitted when the should, balances are updated, and much more.
Protip: With the help of Test Helpers you can emulate the <a href="https://docs.openzeppelin.com/test-helpers/0.5/api#time">passing of time</a> which comes in handy if you have functionality which depends on a certain block height.

Library to help developers test their Smart Contracts written in the Solidity programming language.