Stacks testnet

testnet-follower-conf.toml is a configuration file that you can use for setting genesis balances or configuring event observers. You can grant an address an initial account balance by adding the following entries:

[[ustx_balance]]
address = "ST2VHM28V9E5QCRD6C73215KAPSBKQGPWTEE5CMQT"
amount = 100000000

The address field is the Stacks testnet address, and the amount field is the number of microSTX to grant to it in the genesis block. The addresses of the private keys used in the tutorial below are already added.

Encode and sign transactions

Here, we have generated a keypair that will be used for signing the upcoming transactions:

cargo run --bin blockstack-cli generate-sk --testnet

# Sample output
# {
#  secretKey: "b8d99fd45da58038d630d9855d3ca2466e8e0f89d3894c4724f0efc9ff4b51f001",
#  publicKey: "02781d2d3a545afdb7f6013a8241b9e400475397516a0d0f76863c6742210539b5",
#  stacksAddress: "ST2ZRX0K27GW0SP3GJCEMHD95TQGJMKB7G9Y0X1MH"
# }

This keypair is already registered in the testnet-follower-conf.toml file, so it can be used as presented here.

We will interact with the following simple contract kv-store. In our examples, we will assume this contract is saved locally to ./kv-store.clar:

(define-map store { key: (string-ascii 32) } { value: (string-ascii 32) })

(define-public (get-value (key (string-ascii 32)))
    (match (map-get? store { key: key })
        entry (ok (get value entry))
        (err 0)))

(define-public (set-value (key (string-ascii 32)) (value (string-ascii 32)))
    (begin
        (map-set store { key: key } { value: value })
        (ok true)))

We want to publish this contract on chain, then issue some transactions that interact with it by setting some keys and getting some values, so we can observe read and writes.

Our first step is to generate and sign, using your private key, the transaction that will publish the contract kv-store. To do that, we will use the subcommand:

cargo run --bin blockstack-cli publish --help

With the following arguments:

cargo run --bin blockstack-cli publish b8d99fd45da58038d630d9855d3ca2466e8e0f89d3894c4724f0efc9ff4b51f001 515 0 kv-store ./kv-store.clar --testnet

The 515 is the transaction fee, denominated in microSTX. Right now, the testnet requires one microSTX per byte minimum, and this transaction should be less than 515 bytes. The third argument 0 is a nonce, that must be increased monotonically with each new transaction.

This command will output the binary format of the transaction. In our case, we want to pipe this output and dump it to a file that will be used later in this tutorial.

cargo run --bin blockstack-cli publish b8d99fd45da58038d630d9855d3ca2466e8e0f89d3894c4724f0efc9ff4b51f001 515 0 kv-store ./kv-store.clar --testnet | xxd -r -p > tx1.bin

Publish your contract

Assuming that the testnet is running, we can publish our kv-store contract.

In another terminal (or file explorer), you can move the tx1.bin generated earlier, to the mempool:

curl -X POST -H "Content-Type: application/octet-stream" --data-binary @./tx1.bin https://localhost:20443/v2/transactions

In the terminal window running the testnet, you can observe the state machine's reactions.

Reading from / Writing to the contract

Now that our contract has been published on chain, let's try to submit some read / write transactions. We will start by trying to read the value associated with the key foo.

To do that, we will use the subcommand:

cargo run --bin blockstack-cli contract-call --help

With the following arguments:

cargo run --bin blockstack-cli contract-call b8d99fd45da58038d630d9855d3ca2466e8e0f89d3894c4724f0efc9ff4b51f001 500 1 ST2ZRX0K27GW0SP3GJCEMHD95TQGJMKB7G9Y0X1MH kv-store get-value -e \"foo\" --testnet | xxd -r -p > tx2.bin

contract-call generates and signs a contract-call transaction.

We can submit the transaction by moving it to the mempool path:

curl -X POST -H "Content-Type: application/octet-stream" --data-binary @./tx2.bin https://localhost:20443/v2/transactions

Similarly, we can generate a transaction that would be setting the key foo to the value bar:

cargo run --bin blockstack-cli contract-call b8d99fd45da58038d630d9855d3ca2466e8e0f89d3894c4724f0efc9ff4b51f001 500 2 ST2ZRX0K27GW0SP3GJCEMHD95TQGJMKB7G9Y0X1MH kv-store set-value -e \"foo\" -e \"bar\" --testnet | xxd -r -p > tx3.bin

And submit it by moving it to the mempool path:

curl -X POST -H "Content-Type: application/octet-stream" --data-binary @./tx3.bin https://localhost:20443/v2/transactions

Finally, we can issue a third transaction, reading the key foo again, for ensuring that the previous transaction has successfully updated the state machine:

cargo run --bin blockstack-cli contract-call b8d99fd45da58038d630d9855d3ca2466e8e0f89d3894c4724f0efc9ff4b51f001 500 3 ST2ZRX0K27GW0SP3GJCEMHD95TQGJMKB7G9Y0X1MH kv-store get-value -e \"foo\" --testnet | xxd -r -p > tx4.bin

And submit this last transaction by moving it to the mempool path:

curl -X POST -H "Content-Type: application/octet-stream" --data-binary @./tx4.bin https://localhost:20443/v2/transactions

Congratulations, you can now write your own smart contracts with Clarity.

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