Smart contracts are tested and deployed using a variety of tools, such as Truffle, Remix, and Solc.
Truffle is a development environment, testing framework and asset pipeline for Ethereum, aiming to make life as an Ethereum developer easier. It provides a command line tool to compile, deploy and test smart contracts written in Solidity.
Remix is an online development environment for Solidity smart contracts. It allows developers to write, debug and deploy smart contracts directly in the browser.
Solc is a command line tool that compiles Solidity smart contracts to bytecode that can be deployed to the Ethereum blockchain.
For example, to deploy a smart contract using Truffle, a developer would first write the contract in Solidity, then compile and deploy it using the Truffle command line tool. The developer would then use the Truffle testing framework to write and run tests against the deployed contract. Finally, the contract would be deployed to the Ethereum blockchain.