A testnet is an alternative blockchain network that serves as a staging environment for developers to test their code before rolling out new updates to the mainnet. Expand on testnets and their importance with the example of the Ethereum blockchain.
What is a testnet?
Y test networkshort for “test network”, and translatable to “test network” in French, is a almost identical version to an active blockchain (mainnet), but only dedicated to testing.
In fact, this network intends test new functionalities of a blockchain without cost or risksince the underlying cryptocurrency of this network has no real economic value.
Therefore, a test network use your own cryptocurrencya copy of the original asset, but without having worthless. Using cryptocurrency from a testnet has no impact on the public blockchain, as a testnet is completely isolated from the original chain : It is impossible to transfer cryptocurrencies from a testnet to a mainnet and vice versa.
Therefore, the code of a blockchain can be tested with the testnet. without affecting the active network that hosts the smart contracts and decentralized applications. Also, on a testnet, any user can recover the underlying cryptocurrency at no additional cost, again for testing purposes.
Generally, it is enough to click a button from a dedicated interface to recover a random amount of this cryptocurrency. This is one of the reasons why testnet cryptocurrencies are worthless.
Therefore, a testnet is an environment that allows try new updates before deploying them on the public blockchain. Developers usually do test suites to detect possible errors in the codebugs, and in general to check that everything works correctly.
A product must always be Extensively tested before going into production to certify its correct operation, in any industry. The cryptocurrency industry is no exception and the testnet is the medium through which testing is done.
An update deployed directly to a public blockchain, without having been tested on a testnet, could have dramatic consequences for millions of users in case there are errors in the codeso it’s the responsibility of the developers to make sure this doesn’t happen by using testnets beforehand.
Finally, once the update has been thoroughly tested on a testnet, it can finally be deployed to the mainnet, usually not before a vote of network participants who endorses it
The Ropsten testnet of the Ethereum blockchain
A concrete example of a testnet is Ropsten, an Ethereum blockchain testnet. Launched in November 2016, it is the oldest Ethereum testnet, but there are others such as the Sepolia or Goerli testnet. A blockchain does not necessarily have a single sandbox.
Ethereum developers use the Ropsten testnet to test protocol updates before deploying to the Ethereum mainnet.
This testnet is almost identical to the public Ethereum blockchain, and being a testnet, developers do not have to no need to worry about transaction implications and app testing costs.
Ropsten thus allows developers to access an Ethereum test environment in which errors and failures have very insignificant consequences.
At the time of this writing, the Ropsten testnet is used to testing Ethereum blockchain migration by consensus Work test to a consensus Proof of participation. This famous and long-awaited update, also called The Merge, presents a real technical challenge.
The new version of Ethereum will reduce the energy consumption of the network and make it easier for users to participate in the security of the network, which will consequently increase the level of decentralization, but migrating from Consensus PoS to Consensus PoW is a very complex operation.
Ethereum being to date the main network used for decentralized finance and non-fungible tokens, the slightest mistake not caught before migration could be fatal for the cryptocurrency ecosystem as a whole.
This is how the Ropsten testnet allows developersperform a whole battery of absolutely necessary tests prior to the deployment of this migration on the public Ethereum blockchain.
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The complement of the testnet, the mainnet
A testnet is of no interest without its complement, the main network. All scans performed on a blockchain testnet are for the purpose of deploying the update to the mainnet.
The latter is a network in which real transactions are made and in which the native cryptocurrency has a real economic value. A mainnet is the main and functional blockchain of an ecosystem.
Therefore, the tests carried out on the test network allow to eliminate errors, errors and then implement a functional updateerror-free on the main network.
One of the best known major networks in the cryptocurrency industry is the ethereum mainnetwhich has been updated since 2015 by hard forks like Byzantium (2017), Constantinople (2019), Istanbul (2019) or London (2021) forks.
All these Ethereum protocol updates first being tested on one of the Ethereum testnets so that they are operational and without bugs.
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