Developer environment and a local regtest lab

regtest is a private Bitcoin network that only you can see. Mining is instant, coins are free, and mistakes cost nothing. Every lesson in this path uses it as your lab.

Step 1: Three networks, one program

The same Bitcoin Core program can join three kinds of network. Think of a driving school:

• Mainnet is the highway: real traffic, real money, real consequences. You don't learn here.
• Testnet and signet are a shared practice track. Other learners are on it too, and you wait for its blocks like everyone else.
• Regtest is your own empty car park. Nobody else is there, and a block appears the moment you ask for one.

Two programs do the work. bitcoind is the node itself, running in the background, and bitcoin-cli is how you talk to it. Everything the node knows lives in its data directory, so deleting that folder gives you a brand-new chain.

One rule will surprise you in Step 3: a miner's reward can't be spent until 100 more blocks are built on top of it. Bitcoin calls this coinbase maturity.

Done when: you can say, in your own words, why your first test coins only become spendable after 101 blocks.

Step 2: Install and start a node

Install Bitcoin Core from the official download page, or use a Docker image you trust. Then:

bitcoind -regtest -daemon -fallbackfee=0.0001
bitcoin-cli -regtest getblockchaininfo

Expected: JSON with "chain": "regtest" and "blocks": 0.

Done when: the node answers getblockchaininfo.

Step 3: Mine, fund and check

bitcoin-cli -regtest createwallet "alice"
ADDR=$(bitcoin-cli -regtest -rpcwallet=alice getnewaddress)
bitcoin-cli -regtest generatetoaddress 101 "$ADDR"
bitcoin-cli -regtest -rpcwallet=alice getbalance

Expected: a balance of 50.00000000. You mined 101 blocks, but only the first block's reward has matured.

Try generatetoaddress 1 again and check the balance. Can you predict the new number before you look?

Done when: you can explain why the balance after 101 blocks is 50, not 5,050.

Step 4: Reset

bitcoin-cli -regtest stop
rm -rf ~/.bitcoin/regtest   # on macOS: ~/Library/Application Support/Bitcoin/regtest

Starting from a clean datadir makes experiments repeatable, which is exactly what you want for automated tests later.

Lab evidence

Save these in a notes file; the final project asks for them:

• The output of getblockchaininfo showing "chain": "regtest".
• Your balance after mining 101 blocks, and after one more.
• One sentence on what surprised you.