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How to develop and test a dApp on a local, multi-client testnet

clientsnodessmart contractscomposabilityconsensus layerexecution layertesting
Intermediate
Tedi Mitiku
April 11, 2023
11 minute read minute read

Introduction

This guide walks you through the process of instantiating a configurable local Ethereum testnet, deploying a smart contract to it, and using the testnet to run tests against your dApp. This guide is designed for dApp developers who want to develop and test their dApps locally against different network configurations before deploying to a live testnet or the mainnet.

In this guide, you will:

What is Kurtosis?

Kurtosis(opens in a new tab) is a composable build system designed for configuring multi-container test environments. It specifically enables developers to create reproducible environments that require dynamic setup logic, such as blockchain testnets.

In this guide, the Kurtosis eth-network-package spins up a local Ethereum testnet with support for the geth(opens in a new tab) Execution Layer (EL) client, as well as teku(opens in a new tab), lighthouse(opens in a new tab), and lodestar(opens in a new tab) Consensus Layer (CL) clients. This package serves as a configurable and composable alternative to networks in frameworks like Hardhat Network, Ganache, and Anvil. Kurtosis offers developers greater control and flexibility over the testnets they use, which is a major reason why the Ethereum Foundation used Kurtosis to test the Merge(opens in a new tab) and continues to use it for testing network upgrades.

Setting up Kurtosis

Before you proceed, make sure you have:

Instantiating a local Ethereum testnet

To spin up a local Ethereum testnet, run:

1kurtosis --enclave local-eth-testnet run github.com/kurtosis-tech/eth-network-package
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Note: This command names your network: "local-eth-testnet” using the --enclave flag.

Kurtosis will print the steps its taking under the hood as it works to interpret, validate, and then execute the instructions. At the end, you should see an output that resembles the following:

1INFO[2023-04-04T18:09:44-04:00] ======================================================
2INFO[2023-04-04T18:09:44-04:00] ||          Created enclave: local-eth-testnet      ||
3INFO[2023-04-04T18:09:44-04:00] ======================================================
4Name:            local-eth-testnet
5UUID:            39372d756ae8
6Status:          RUNNING
7Creation Time:   Tue, 04 Apr 2023 18:09:03 EDT
8
9========================================= Files Artifacts =========================================
10UUID           Name
11d4085a064230   cl-genesis-data
121c62cb792e4c   el-genesis-data
13bd60489b73a7   genesis-generation-config-cl
14b2e593fe5228   genesis-generation-config-el
15d552a54acf78   geth-prefunded-keys
165f7e661eb838   prysm-password
17054e7338bb59   validator-keystore-0
18
19========================================== User Services ==========================================
20UUID           Name                                           Ports                                         Status
21e20f129ee0c5   cl-client-0-beacon                             http: 4000/tcp -> <http://127.0.0.1:54261>    RUNNING
22                                                              metrics: 5054/tcp -> <http://127.0.0.1:54262>
23                                                              tcp-discovery: 9000/tcp -> 127.0.0.1:54263
24                                                              udp-discovery: 9000/udp -> 127.0.0.1:60470
25a8b6c926cdb4   cl-client-0-validator                          http: 5042/tcp -> 127.0.0.1:54267             RUNNING
26                                                              metrics: 5064/tcp -> <http://127.0.0.1:54268>
27d7b802f623e8   el-client-0                                    engine-rpc: 8551/tcp -> 127.0.0.1:54253       RUNNING
28                                                              rpc: 8545/tcp -> 127.0.0.1:54251
29                                                              tcp-discovery: 30303/tcp -> 127.0.0.1:54254
30                                                              udp-discovery: 30303/udp -> 127.0.0.1:53834
31                                                              ws: 8546/tcp -> 127.0.0.1:54252
32514a829c0a84   prelaunch-data-generator-1680646157905431468   <none>                                        STOPPED
3362bd62d0aa7a   prelaunch-data-generator-1680646157915424301   <none>                                        STOPPED
3405e9619e0e90   prelaunch-data-generator-1680646157922872635   <none>                                        STOPPED
35
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Congratulations! You used Kurtosis to instantiate a local Ethereum testnet, with a CL (lighthouse) and EL client (geth), over Docker.

Review

In this section, you executed a command that directed Kurtosis to use the eth-network-package hosted remotely on GitHub(opens in a new tab) to spin up a local Ethereum testnet within a Kurtosis Enclave(opens in a new tab). Inside your enclave, you will find both "file artifacts" and "user services".

The File Artifacts(opens in a new tab) in your enclave include all the data generated and utilized to bootstrap the EL and CL clients. The data was created using the prelaunch-data-generator service built from this Docker image(opens in a new tab)

User services display all the containerized services operating in your enclave. You will notice that a single node, featuring both an EL client and a CL client, has been created.

Connect your dApp development environment to the local Ethereum testnet

Setup the dApp development environment

Now that you have a running local testnet, you can connect your dApp development environment to use your local testnet. The Hardhat framework will be used in this guide to deploy a blackjack dApp to your local testnet.

To set up your dApp development environment, clone the repository that contains our sample dApp and install its dependencies, run:

1git clone https://github.com/kurtosis-tech/awesome-kurtosis.git && cd awesome-kurtosis/smart-contract-example && yarn
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The smart-contract-example(opens in a new tab) folder used here contains the typical setup for a dApp developer using the Hardhat(opens in a new tab) framework:

Configure Hardhat to use the local testnet

With your dApp development environment set up, you will now connect Hardhat to use the local Ethereum testnet generated using Kurtosis. To accomplish this, replace <$YOUR_PORT> in the localnet struct in your hardhat.config.ts config file with the port of the rpc uri output from any el-client-<num> service. In this sample case, the port would be 64248. Your port will be different.

Example in hardhat.config.ts:

1localnet: {
2url: 'http://127.0.0.1:<$YOUR_PORT>',// TODO: REPLACE $YOUR_PORT WITH THE PORT OF A NODE URI PRODUCED BY THE ETH NETWORK KURTOSIS PACKAGE
3
4// These are private keys associated with prefunded test accounts created by the eth-network-package
5// <https://github.com/kurtosis-tech/eth-network-package/blob/main/src/prelaunch_data_generator/genesis_constants/genesis_constants.star>
6accounts: [
7    "ef5177cd0b6b21c87db5a0bf35d4084a8a57a9d6a064f86d51ac85f2b873a4e2",
8    "48fcc39ae27a0e8bf0274021ae6ebd8fe4a0e12623d61464c498900b28feb567",
9    "7988b3a148716ff800414935b305436493e1f25237a2a03e5eebc343735e2f31",
10    "b3c409b6b0b3aa5e65ab2dc1930534608239a478106acf6f3d9178e9f9b00b35",
11    "df9bb6de5d3dc59595bcaa676397d837ff49441d211878c024eabda2cd067c9f",
12    "7da08f856b5956d40a72968f93396f6acff17193f013e8053f6fbb6c08c194d6",
13  ],
14},
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Once you save your file, your Hardhat dApp development environment is now connected to your local Ethereum testnet! You can verify that your testnet is working by running:

1npx hardhat balances --network localnet
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The output should look something like this:

10x878705ba3f8Bc32FCf7F4CAa1A35E72AF65CF766 has balance 10000000000000000000000000
20x4E9A3d9D1cd2A2b2371b8b3F489aE72259886f1A has balance 10000000000000000000000000
30xdF8466f277964Bb7a0FFD819403302C34DCD530A has balance 10000000000000000000000000
40x5c613e39Fc0Ad91AfDA24587e6f52192d75FBA50 has balance 10000000000000000000000000
50x375ae6107f8cC4cF34842B71C6F746a362Ad8EAc has balance 10000000000000000000000000
60x1F6298457C5d76270325B724Da5d1953923a6B88 has balance 10000000000000000000000000
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This confirms that Hardhat is using your local testnet and detects the pre-funded accounts created by the eth-network-package.

Deploy and test your dApp locally

With the dApp development environment fully connected to the local Ethereum testnet, you can now run development and testing workflows against your dApp using the local testnet.

To compile and deploy the ChipToken.sol smart contract for local prototyping and development, run:

1npx hardhat compile
2npx hardhat run scripts/deploy.ts --network localnet
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The output should look something like:

1ChipToken deployed to: 0xAb2A01BC351770D09611Ac80f1DE076D56E0487d
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Now try running the simple.js test against your local dApp to confirm each player in our Blackjack dApp has 1000 minted for them:

The output should look something like this:

1npx hardhat test --network localnet
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The output should look something like this:

1ChipToken
2    mint
3      ✔ should mint 1000 chips for PLAYER ONE
4
5  1 passing (654ms)
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Review

At this point, you’ve now set up a dApp development environment, connected it to a local Ethereum network created by Kurtosis, and have compiled, deployed, and ran a simple test against your dApp.

Now let’s explore how you can configure the underlying network for testing our dApps under varying network configurations.

Configuring the local Ethereum testnet

Changing the client configurations and number of nodes

Your local Ethereum testnet can be configured to use different EL and CL client pairs, as well as a varying number of nodes, depending on the scenario and specific network configuration you want to develop or test. This means that, once set up, you can spin up a customized local testnet and use it to run the same workflows (deployment, tests, etc.) under various network configurations to ensure everything works as expected. To learn more about the other parameters you can modify, visit this link.

Give it a try! You can pass various configuration options to the eth-network-package via a JSON file. This network params JSON file provides the specific configurations that Kurtosis will use to set up the local Ethereum network.

Take the default configuration file and edit it to spin up two nodes with different EL/CL pairs:

  • Node 1 with geth/lighthouse
  • Node 2 with geth/lodestar
  • Node 3 with geth/teku

This configuration creates a heterogeneous network of Ethereum node implementations for testing your dApp. Your configuration file should now look like:

1{
2  "participants":
3    [
4      {
5        "el_client_type": "geth",
6        "el_client_image": "",
7        "el_client_log_level": "",
8        "cl_client_type": "lighthouse",
9        "cl_client_image": "",
10        "cl_client_log_level": "",
11        "beacon_extra_params": [],
12        "el_extra_params": [],
13        "validator_extra_params": [],
14        "builder_network_params": null,
15      },
16      {
17        "el_client_type": "geth",
18        "el_client_image": "",
19        "el_client_log_level": "",
20        "cl_client_type": "lodestar",
21        "cl_client_image": "",
22        "cl_client_log_level": "",
23        "beacon_extra_params": [],
24        "el_extra_params": [],
25        "validator_extra_params": [],
26        "builder_network_params": null,
27      },
28      {
29        "el_client_type": "geth",
30        "el_client_image": "",
31        "el_client_log_level": "",
32        "cl_client_type": "teku",
33        "cl_client_image": "",
34        "cl_client_log_level": "",
35        "beacon_extra_params": [],
36        "el_extra_params": [],
37        "validator_extra_params": [],
38        "builder_network_params": null,
39      },
40    ],
41  "network_params":
42    {
43      "preregistered_validator_keys_mnemonic": "giant issue aisle success illegal bike spike question tent bar rely arctic volcano long crawl hungry vocal artwork sniff fantasy very lucky have athlete",
44      "num_validator_keys_per_node": 64,
45      "network_id": "3151908",
46      "deposit_contract_address": "0x4242424242424242424242424242424242424242",
47      "seconds_per_slot": 12,
48      "genesis_delay": 120,
49      "capella_fork_epoch": 5,
50    },
51}
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Each participants struct maps to a node in the network, so 3 participants structs will tell Kurtosis to spin up 3 nodes in your network. Each participants struct will allow you to specify the EL and CL pair used for that specific node.

The network_params struct configures the network settings that are used to create the genesis files for each node as well as other settings like the seconds per slot of the network.

Save your edited params file in any directory you wish (in the example below, it is saved to the desktop) and then use it to run your Kurtosis package by running:

1kurtosis clean -a && kurtosis run --enclave local-eth-testnet github.com/kurtosis-tech/eth-network-package "$(cat ~/eth-network-params.json)"
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Note: the kurtosis clean -a command is used here to instruct Kurtosis to destroy the old testnet and its contents before starting a new one up.

Again, Kurtosis will work for a bit and print out the individual steps that are taking place. Eventually, the output should look something like:

1Starlark code successfully run. No output was returned.
2INFO[2023-04-07T11:43:16-04:00] ==========================================================
3INFO[2023-04-07T11:43:16-04:00] ||          Created enclave: local-eth-testnet          ||
4INFO[2023-04-07T11:43:16-04:00] ==========================================================
5Name:            local-eth-testnet
6UUID:            bef8c192008e
7Status:          RUNNING
8Creation Time:   Fri, 07 Apr 2023 11:41:58 EDT
9
10========================================= Files Artifacts =========================================
11UUID           Name
12cc495a8e364a   cl-genesis-data
137033fcdb5471   el-genesis-data
14a3aef43fc738   genesis-generation-config-cl
158e968005fc9d   genesis-generation-config-el
163182cca9d3cd   geth-prefunded-keys
178421166e234f   prysm-password
18d9e6e8d44d99   validator-keystore-0
1923f5ba517394   validator-keystore-1
204d28dea40b5c   validator-keystore-2
21
22========================================== User Services ==========================================
23UUID           Name                                           Ports                                            Status
24485e6fde55ae   cl-client-0-beacon                             http: 4000/tcp -> http://127.0.0.1:65010         RUNNING
25                                                              metrics: 5054/tcp -> http://127.0.0.1:65011
26                                                              tcp-discovery: 9000/tcp -> 127.0.0.1:65012
27                                                              udp-discovery: 9000/udp -> 127.0.0.1:54455
2873739bd158b2   cl-client-0-validator                          http: 5042/tcp -> 127.0.0.1:65016                RUNNING
29                                                              metrics: 5064/tcp -> http://127.0.0.1:65017
301b0a233cd011   cl-client-1-beacon                             http: 4000/tcp -> 127.0.0.1:65021                RUNNING
31                                                              metrics: 8008/tcp -> 127.0.0.1:65023
32                                                              tcp-discovery: 9000/tcp -> 127.0.0.1:65024
33                                                              udp-discovery: 9000/udp -> 127.0.0.1:56031
34                                                              validator-metrics: 5064/tcp -> 127.0.0.1:65022
35949b8220cd53   cl-client-1-validator                          http: 4000/tcp -> 127.0.0.1:65028                RUNNING
36                                                              metrics: 8008/tcp -> 127.0.0.1:65030
37                                                              tcp-discovery: 9000/tcp -> 127.0.0.1:65031
38                                                              udp-discovery: 9000/udp -> 127.0.0.1:60784
39                                                              validator-metrics: 5064/tcp -> 127.0.0.1:65029
40c34417bea5fa   cl-client-2                                    http: 4000/tcp -> 127.0.0.1:65037                RUNNING
41                                                              metrics: 8008/tcp -> 127.0.0.1:65035
42                                                              tcp-discovery: 9000/tcp -> 127.0.0.1:65036
43                                                              udp-discovery: 9000/udp -> 127.0.0.1:63581
44e19738e6329d   el-client-0                                    engine-rpc: 8551/tcp -> 127.0.0.1:64986          RUNNING
45                                                              rpc: 8545/tcp -> 127.0.0.1:64988
46                                                              tcp-discovery: 30303/tcp -> 127.0.0.1:64987
47                                                              udp-discovery: 30303/udp -> 127.0.0.1:55706
48                                                              ws: 8546/tcp -> 127.0.0.1:64989
49e904687449d9   el-client-1                                    engine-rpc: 8551/tcp -> 127.0.0.1:64993          RUNNING
50                                                              rpc: 8545/tcp -> 127.0.0.1:64995
51                                                              tcp-discovery: 30303/tcp -> 127.0.0.1:64994
52                                                              udp-discovery: 30303/udp -> 127.0.0.1:58096
53                                                              ws: 8546/tcp -> 127.0.0.1:64996
54ad6f401126fa   el-client-2                                    engine-rpc: 8551/tcp -> 127.0.0.1:65003          RUNNING
55                                                              rpc: 8545/tcp -> 127.0.0.1:65001
56                                                              tcp-discovery: 30303/tcp -> 127.0.0.1:65000
57                                                              udp-discovery: 30303/udp -> 127.0.0.1:57269
58                                                              ws: 8546/tcp -> 127.0.0.1:65002
5912d04a9dbb69   prelaunch-data-generator-1680882122181135513   <none>                                           STOPPED
605b45f9c0504b   prelaunch-data-generator-1680882122192182847   <none>                                           STOPPED
613d4aaa75e218   prelaunch-data-generator-1680882122201668972   <none>                                           STOPPED
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Congratulations! You’ve successfully configured your local testnet to have 3 nodes instead of 1. To run the same workflows you did before against your dApp (deploy & test), perform the same operations we did before by replacing the <$YOUR_PORT> in the localnet struct in your hardhat.config.ts config file with the port of the rpc uri output from any el-client-<num> service in your new, 3-node local testnet.

Conclusion

And that's it! To recap this short guide, you:

  • Created a local Ethereum testnet over Docker using Kurtosis
  • Connected your local dApp development environment to the local Ethereum network
  • Deployed a dApp and ran a simple test against it on the local Ethereum network
  • Configured the underlying Ethereum network to have 3 nodes

We’d love to hear from you on what went well for you, what could be improved, or to answer any of your questions. Don’t hesitate to reach out via GitHub(opens in a new tab) or email us(opens in a new tab)!

Other examples and guides

We encourage you to check out our quickstart(opens in a new tab) (where you’ll build a Postgres database and API on top) and our other examples in our awesome-kurtosis repository(opens in a new tab) where you’ll find some great examples, including packages for:

Last edit: @pettinarip(opens in a new tab), October 10, 2023

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