Simulator UI Overview

The Simulator UI gives you an IDE-like experience when simulating transactions. You can either build a transaction from scratch or load an existing transaction into Transaction Simulator, tweak the inputs, and override state variables or the smart contract code.

Replaying an existing transaction using a simulation allows you to:

• Access decoded transaction trace, 100% accurate gas usage overview, asset and balance changes, and storage modifications.
• Validate bugfixes by running simulations on modified smart contract source code.
• Validate adjustments to transaction parameters to find optimal inputs.
• Troubleshoot an existing transaction, either a reverted one or a successful transaction with undesired effects.

Using the Simulator UI

You can use the Simulator UI to:

• Simulate a simple transaction
• Set custom overrides of smart contract variables to impose custom conditions on the simulation.
• Progress to using Simulation API to do simulations programmatically.
• Explore using Forks to simulate several transactions.

Building a simulation

When building a transaction simulation, you can:

• Run a simulation off of an existing transaction by clicking Re-Simulate button on Inspect Transaction page. By default, the simulation executes on the block and timestamp of the original transaction.
• Build a simulation scratch, by choosing a contract, method to call, and arguments to pass.
• Use either the latest block number or specify a historical block number.
• Run a simulation on changed smart contract source code.
• Override smart contract state variables.
• Override a block header by specifying custom blockNumber and timestamp values that the smart contract code receives through block.number and block.timestamp respectively.
• Specify an arbitrary sender (from).
• Specify an arbitrary gas and gasPrice for this particular simulation.