How to Simulate Transactions with Tenderly SDK

In this tutorial, you’ll learn how to run a transaction simulation using the Tenderly SDK. Simulations allow you to test the behavior of your transactions without sending them on-chain. Learn more about Tenderly’s Transaction Simulator here.

Prerequisites

• Node.js installed on your machine
• Tenderly account with an API key
• Project set up in the Tenderly Dashboard

Step 1: Initialize a new Node.js project

Create a new directory for your project, navigate to it in the terminal, and initialize a new Node.js project:

mkdir tenderly-simulation
cd tenderly-simulation
npm init -y

Step 2: Install Tenderly SDK

Install the Tenderly SDK npm package as a dependency in your Node.js project:

npm install @tenderly/sdk

Step 3: Import the Tenderly SDK and configure it

Create a new file named index.js in your project directory, and add the following code to import the Tenderly SDK and configure it with your Tenderly account details:

const { Network, Tenderly } = require('@tenderly/sdk');
 
const tenderly = new Tenderly({
  accountName: 'your-account-name',
  projectName: 'your-project-name',
  accessKey: 'your-access-key',
  network: Network.MAINNET, // Replace with the appropriate network
});

Make sure to replace your-account-name, your-project-name, and your-access-key with your actual Tenderly account information.

Step 4: Define the transaction details

Next, define the transaction details for the simulation.

Add the following code to index.js:

const transactionParameters = {
  from: '0x0000000000000000000000000000000000000000',
  to: '0x1f98431c8ad98523631ae4a59f267346ea31f984',
  input: '0xa1671295000000000000000000000000dac17f958d2ee523a2206206994597c13d831ec7000000000000000000000000152649ea73beab28c5b49b26eb48f7ead6d4c8980000000000000000000000000000000000000000000000000000000000000bb8',
  value: '0',
  gas: 8000000,
  gas_price: '0',
};
 
const simulation = {
  transaction: transactionParameters,
  blockNumber: 18813657, // simulation's target block number
  //overrides: {...} // optional state overrides field
};
 

Replace the from, to, input, value, gas, and gas_price fields with your desired transaction details. The override field is optional and allows you to override the state of specific contracts in the simulation.

Step 5: Run the transaction simulation

Now, use the Tenderly SDK’s simulateTransaction method to run the transaction simulation.

Add the following code to index.js:

(async () => {
  try {
    const simulationResult = await tenderly.simulator.simulateTransaction(simulationDetails);
    console.log('Simulation result:', simulationResult);
  } catch (error) {
    console.error('Error running simulation:', error);
  }
})();

This code runs an asynchronous function that calls the simulateTransaction method and logs the simulation result to the console.

Step 6: Execute the script

Save the index.js file and run the script using the following command:

node index.js

If the transaction simulation is successful, you’ll see the simulation result printed in the console.

That’s it! You’ve now learned how to run a transaction simulation using the Tenderly SDK.