Testing Applications

Bitcoin Core provides testing tools designed to let developers test their applications with reduced risks and limitations.

Testnet

When run with no arguments, all Bitcoin Core programs default to Bitcoin’s main network (mainnet). However, for development, it’s safer and cheaper to use Bitcoin’s test network (testnet) where the satoshis spent have no real-world value. Testnet also relaxes some restrictions (such as standard transaction checks) so you can test functions which might currently be disabled by default on mainnet.

To use testnet, use the argument -testnet with bitcoin-cli, bitcoind or bitcoin-qt or add testnet=1 to your bitcoin.conf file as described earlier. To get free satoshis for testing, use Piotr Piasecki’s testnet faucet. Testnet is a public resource provided for free by members of the community, so please don’t abuse it.

Regtest Mode

For situations where interaction with random peers and blocks is unnecessary or unwanted, Bitcoin Core’s regression test mode (regtest mode) lets you instantly create a brand-new private block chain with the same basic rules as testnet—but one major difference: you choose when to create new blocks, so you have complete control over the environment.

Many developers consider regtest mode the preferred way to develop new applications. The following example will let you create a regtest environment after you first configure bitcoind.

> bitcoind -regtest -daemon
Bitcoin server starting

Start bitcoind in regtest mode to create a private block chain.

## Bitcoin Core 0.10.1 and earlier
bitcoin-cli -regtest setgenerate true 101

## Bitcoin Core 17.1 and earlier
bitcoin-cli -regtest generate 101

## Bitcoin Core 18.0 and later
bitcoin-cli -regtest generatetoaddress 101 $(bitcoin-cli -regtest getnewaddress)

Generate 101 blocks using a special RPC which is only available in regtest mode. This takes less than a second on a generic PC. Because this is a new block chain using Bitcoin’s default rules, the first blocks pay a block reward of 50 bitcoins. Unlike mainnet, in regtest mode only the first 150 blocks pay a reward of 50 bitcoins. However, a block must have 100 confirmations before that reward can be spent, so we generate 101 blocks to get access to the coinbase transaction from block #1.

If block generation fails, check the RPC error code and message first. The following table lists common regtest setup errors and how to resolve them:

Error	Likely cause	Resolution
bad-fork-prior-to-checkpoint (code 67)	The command is running against a chain with mainnet or testnet validation rules, or the data directory contains state from the wrong network.	Restart both bitcoind and bitcoin-cli with -regtest. If this is a disposable test environment, stop Bitcoin Core, delete only the regtest subdirectory from the Bitcoin Core data directory, and start again.
Method not found (code -32601)	The example command is not supported by the Bitcoin Core version you are running.	For Bitcoin Core 18.0 and later, use generatetoaddress with an address returned by bitcoin-cli -regtest getnewaddress. Older nodes may require generate or setgenerate as shown above.
Requested wallet does not exist or is not loaded (code -18)	getnewaddress was called before creating or loading a wallet.	Create or load a regtest wallet, for example bitcoin-cli -regtest createwallet testwallet, then rerun getnewaddress and generatetoaddress.
Loading block index (code -28)	The node is still starting.	Wait until startup finishes, then retry the command.
Insufficient funds (code -6)	A transaction is spending coinbase outputs before they have matured.	Mine 101 blocks before spending the first coinbase reward.

bitcoin-cli -regtest getbalance
50.00000000

Verify that we now have 50 bitcoins available to spend.

You can now use Bitcoin Core RPCs prefixed with bitcoin-cli -regtest.

Regtest wallets and block chain state (chainstate) are saved in the regtest subdirectory of the Bitcoin Core configuration directory. You can safely delete the regtest subdirectory and restart Bitcoin Core to start a new regtest. (See the Developer Examples Introduction for default configuration directory locations on various operating systems. Always back up mainnet wallets before performing dangerous operations such as deleting.)