Bitcoin: Understanding the Difference Between Testnets and Mainnets Using PSBT
As Bitcoin developers and users, we have all come across the terminology “testnet” and “mainnet.” While both refer to the underlying blockchain network, they are different in many ways. In this article, we will look at what it means for a testnet versus a mainnet to be written as public scriptable binary tar files (PSBTs), explore their differences, and discuss whether covering all edge cases with unit tests on the mainnet is sufficient.
Testnets vs. Mainnets: What’s the Difference?
A testnet is a simulated blockchain network used by developers to test new features, networks, or scripts without affecting the live mainnet. It is essentially a copy of the mainnet with a few modifications or differences to facilitate testing and experimentation. Testnets are often created using tools like [Bitcoin-Testnet]( or [testnet-btcscan]( The goal is to test scripts, wallets, and other components without impacting the mainnet.
On the other hand, a mainnet (also called a production network) refers to the actual blockchain network that users interact with on a daily basis. It is the actual implementation of Bitcoin, where transactions are verified by nodes around the world and miners validate them using powerful computers.
PSBT: A Key Component
Public Scriptable Binary Tar (PSBT) files are a file format used to represent smart contracts or scripts on the Bitcoin network. They contain the serialized data of the sender and receiver of a transaction in binary format, as well as metadata such as block hashes and timestamps. PSBTs are essentially digital files that can be easily copied and pasted into other contexts.
Testnets vs. Mainnet PSBTs: What’s the Difference?
Here’s where things get interesting:
- Script Execution: When you run a script on a testnet, it runs in a simulated blockchain environment. However, since the testnet is not the live mainnet, this does not affect the actual execution of the script or the result.
- Node Behavior: In a testnet, nodes are configured differently to simulate specific behaviors or constraints (e.g., reduced transaction fees). This allows developers to test scripts that might require such customizations on the real mainnet.
On the other hand:
- Mainnet PSBTs contain real Bitcoin transactions: When you create and run a script on the mainnet, it includes all the information needed to verify and process transactions. Mainnet PSBTs represent these transactions in binary format.
- Realistic node behavior: Mainnet nodes are designed to interact with real-world blockchain data, which means they will behave differently when running scripts. This can lead to more realistic results or unexpected behavior.
Covering edge cases with unit testing
While testing on the mainnet is essential to ensure that your script works as expected, covering all edge cases through unit testing alone may not be enough. Here’s why:
- Edge cases are unpredictable: Even with thorough testing, you may miss critical edge cases that occur rarely or unexpectedly.
- Simulation vs. real-world behavior: Testnets are simulations, but mainnet nodes behave differently due to various factors such as transaction fees, block time, and network congestion.
To ensure that your script works properly on both testnets and the mainnet, it is essential to:
- Test on a variety of networks: Use different testnets (e.g., [Bitcoin-Testnet]( to simulate various conditions.
- Use real data: When testing on the mainnet, use real blockchain data and transaction information to verify the behavior of your script.