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State overrides set custom values for a contract’s storage before a simulation executes. Use them to satisfy access-control checks, plant balances, or set any storage slot to the value your scenario needs, without owning the keys or state on the real network. This page walks through a complete example. For the field-level reference of the State overrides cheatcode, see Simulation Parameters.

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Example: minting 2 DAI

We’ll simulate minting 2 DAI (2000000000000000000 wei) to the holder 0xe58b9ee93700a616b50509c8292977fa7a0f8ce1, sent from 0xe2e2e2e2e2e2e2e2e2e2e2e2e2e2e2e2e2e2e2e2. DAI’s mint function is guarded by a wards mapping: only registered ward addresses can mint. The sender is not a ward on Mainnet, so a plain simulation reverts. The override wards[0xe2e2…e2e2] = 1 makes it a ward for the duration of the simulation.

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Build the mint step

  1. Go to Simulator and click New Simulation.
  2. In the Contract field, paste 0x6b175474e89094c44da98b954eedeac495271d0f and select Dai.
  3. Select mint in the Function field.
  4. Set usr to 0xe58b9ee93700a616b50509c8292977fa7a0f8ce1 and wad to 2000000000000000000.
  5. Set the step’s From to 0xe2e2e2e2e2e2e2e2e2e2e2e2e2e2e2e2e2e2e2e2.

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Add the state override

  1. Expand the State overrides section below the step fields and click Add State Override. The override’s contract defaults to the step’s target (Dai).
  2. Under Storage variables, enter the key wards[0xe2e2e2e2e2e2e2e2e2e2e2e2e2e2e2e2e2e2e2e2] and the value 1. The key field suggests the contract’s decoded storage variables (wards[], balanceOf[], totalSupply, and so on); fill the mapping key inside the brackets.
  3. Click the + button next to the value to add the pair. The committed pair appears as a row under Storage variables. Tenderly stores it as the computed storage slot hash.
Step editor with Dai mint function, usr and wad arguments filled, and the State overrides section showing the committed wards mapping override
The override pair must be committed with the + button. An uncommitted key/value entry is treated as invalid and the simulation will not start.
To override the contract’s native balance instead of (or in addition to) storage, flip the Use custom balance switch in the same section.

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Run and inspect

  1. Click Simulate. The mint executes successfully because the simulation sees the sender as a ward.
Simulation result showing Status Success for mint(), an ERC-20 transfer row crediting 2 DAI, and the decoded execution trace
The result tabs confirm what the override changed:
  • The Events tab shows the Transfer event from the zero address to the holder for 2000000000000000000 wei.
Events tab showing the decoded Transfer event with src, dst, and wad fields
  • The State tab lists the applied State Overrides (the ward slot set to 1) and the resulting State Changes: the holder’s balanceOf going from 0 to 2000000000000000000, the increased totalSupply, and the sender’s nonce.
State tab showing the wards storage slot override under State Overrides and the balanceOf and totalSupply changes under State Changes

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Raw storage keys

Instead of the decoded mapping[key] form, you can enter the raw 32-byte storage slot directly. For a Solidity mapping at storage position p, the slot for mapping[k] is keccak256(abi.encode(k, p)). The wards override above resolves to: 
0xedd7d04419e9c48ceb6055956cbb4e2091ae310313a4d1fa7cbcfe7561616e03
Raw keys are the only option for contracts without verified source, and they match the format used by the Simulation API’s state overrides and the bundle guide.

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Persisting overridden state

Simulations are stateless: the override applies to one run. To keep modified state as a persistent environment you can transact against repeatedly, use Virtual Environments.