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Bitcoin: Understanding the Differences Between Testnets and Mainnets with PSBT
As Bitcoin developers and users, we’ve all come across the terms “testnet” and “mainnet.” While both terms refer to the underlying blockchain network, they differ in many ways. In this article, we’ll take a closer look at what the Public Scriptable Binary Tarball (PSBT) records for the testnet and mainnet, analyze the differences between them, and consider whether it’s sufficient to cover all edge cases with unit testing on the mainnet.
Testnet vs. Mainnet: What’s the Difference?
A testnet is a simulated blockchain network used by developers to test new features, networks, or scripts without impacting the live mainnet. It’s essentially a copy of the mainnet with some modifications and differences to make testing and experimenting easier. Testnets are often created using tools like [Bitcoin-Testnet]( or [testnet-btcscan]( The goal is to test scripts, wallets, and other components without affecting the mainnet.
On the other hand, the mainnet (also known as the production network) refers to the actual blockchain network that users interact with on a daily basis. This is the real implementation of Bitcoin, where transactions are verified by nodes around the world and confirmed by miners using powerful computers.
PSBT: A Key Element
Public Scriptable Binary Tarballs (PSBT) is a file format used to represent smart contracts and scripts on the Bitcoin network. They contain serialized transaction sender and receiver data in binary format, as well as metadata such as block hashes and timestamps. PSBT files are essentially digital files that can be easily copied and pasted into other contexts.
Testnet vs. Mainnet PSBT: What’s the Difference?
Here’s where it gets interesting:
- Script Execution: When you run a script on the testnet, it executes in a simulated blockchain environment. However, since the testnet is not the current mainnet, this has no impact on the actual execution or results of the script.
- Node Behavior
: On the testnet, nodes are configured differently to simulate certain behaviors or limitations (e.g. lower transaction fees). This allows developers to test scripts that may require such changes on the actual mainnet.
On the other hand:
- Mainnet PSBTs contain actual Bitcoin transactions: When you create and run a script on the mainnet, it contains all the necessary data to verify and process transactions. The mainnet PSBT represents these transactions in binary format.
- Real-world node behavior: Mainnet nodes are designed to interact with real blockchain data, meaning they will behave differently when executing scripts. This can lead to more realistic results or unexpected behavior.
Covering edge cases through unit testing
While mainnet testing is crucial to ensuring that your script works as expected, simply covering all edge cases through unit testing may not be enough. Here’s why:
- Edge cases are unpredictable: Even with thorough testing, you can miss critical edge cases that happen infrequently or unexpectedly.
- Simulation vs. real-world behavior: Testnets are simulations, but mainnet nodes behave differently due to various factors, such as transaction fees, block times, and network congestion.
To ensure that your script will work properly on both testnets and mainnets, you should do the following:
- Test on different networks: Use different testnets (e.g. [Bitcoin-Testnet]( to simulate different conditions.
- Use real data: When testing on the mainnet, use real blockchain and transaction data to verify the behavior of your script.
