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.

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.

Troubleshooting block generation

If block generation fails, check the exact RPC error before changing your test state. The numeric code in a JSON-RPC response is not always the same thing as a validation reject code printed inside the error message.

Error	Likely cause	Resolution
Method not found or error code: -32601 when using setgenerate or generate	The mining RPC changed between Bitcoin Core releases. The generate RPC has been unavailable since Bitcoin Core 18.0.	Use the command shown above for your Bitcoin Core version. For Bitcoin Core 18.0 and later, use generatetoaddress with a regtest address.
No wallet is loaded or error code: -18 from getnewaddress	Recent Bitcoin Core versions do not always create or load a default wallet automatically.	Create or load a regtest wallet, for example bitcoin-cli -regtest createwallet "regtest", then request an address with bitcoin-cli -regtest -rpcwallet=regtest getnewaddress.
Error: Invalid address or error code: -5 from generatetoaddress	The address is missing, mistyped, or belongs to another network.	Use an address produced by the same regtest node and wallet. Mainnet, testnet, and signet addresses are not valid regtest mining targets.
CreateNewBlock: TestBlockValidity failed: bad-fork-prior-to-checkpoint (code 67)	The block template failed block validation before mining. The code 67 text is the validation reject code included in the message, not a JSON-RPC method code.	Confirm that both bitcoind and bitcoin-cli are using -regtest and the same data directory. If the error continues in a disposable test environment, stop Bitcoin Core and start from a fresh regtest chain by deleting only the regtest subdirectory or by using a new -datadir.

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.)