Using Forks UI

The following guide shows you how to create a Fork using the Tenderly Dashboard. Once you create the Fork, you can simulate transactions.

In this example, we’ll simulate:

1. TX1 – mint: We’ll use an arbitrary address to mint 2 DAI for 0xe58b9ee93700a616b50509c8292977fa7a0f8ce1 .
2. TX2 – approve: The address 0xe58b9ee93700a616b50509c8292977fa7a0f8ce1 will approve 0xf7ddedc66b1d482e5c38e4730b3357d32411e5dd to spend 0.5 DAI.
3. TX3 – transferFrom: Тhe address we just approved (0xf7ddedc66b1d482e5c38e4730b3357d32411e5dd) will transfer 0.25 DAI to 0xbd8daa414fda8a8a129f7035e7496759c5af8570.

Create a Fork

First, from the navigation menu on your left, select Forks and then:

• Click the Create Fork button.
• Select the network you’d like to fork.
• Name your Fork as you like.
• Choose a specific block number if needed.

Alternatively, you can use the Fork API to create a Fork programmatically.

After creating a Fork, you can use:

• The Fork UI to send transactions in an IDE-like environment.
• The Fork RPC to send transactions via Ethers.js.

The Fork exposes JSON RPC access. The RPC link is located in the Fork header.

TX1: Simulate DAI minting with state overrides

First, we need to mint 2 DAI (2000000000000000000 wei) for 0xe58b9ee93700a616b50509c8292977fa7a0f8ce1. We’ll use the address 0xf2f2f2f2f2f2f2f2f2f2f2f2f2f2f2f2f2f2f2f2 as the minter.

Since this isn’t an actual ward on Mainnet DAI, we’ll have to use state overrides to make it a ward during the simulation.

To complete this, follow these steps:

Step 1: Click the New Simulation button.

Step 2: Select the Dai contract from the dropdown.

Step 3: Select the mint function from the Function dropdown.

Step 4: Paste into the usr field 0xe58b9ee93700a616b50509c8292977fa7a0f8ce1 as the address of the receiver of the minted DAI.

Step 5: Paste 2000000000000000000into thewadfield, as the amount.

Step 6: Paste 0xf2f2f2f2f2f2f2f2f2f2f2f2f2f2f2f2f2f2f2f2 into the from field on the right. This is the address that will pretend to be able to mint.

Next, you need to complete the state override.

If you check the source of the DAI contract, you’ll see the wards mapping from an address to a number. Essentially, for minting to work, we have to plant 0xf2...f2 as a ward. This is the exact state override we must complete.

wards[0xf2f2f2f2f2f2f2f2f2f2f2f2f2f2f2f2f2f2f2f2] = 1

Step 7: Scroll down and click State Overrides and then Add State Override.

Step 8: Select the Dai contract from the dropdown.

Step 9: Scroll to Storage variables and click the Add more button.

Step 10: In the key field, paste the left-hand side of the ward assignment (wards[0xf2f2f2f2f2f2f2f2f2f2f2f2f2f2f2f2f2f2f2f2]).

Step 11: In the value field, paste the right-hand side of the ward assignment (1).

Step 12: Click Simulate.

Now, the account 0xe58b9ee93700a616b50509c8292977fa7a0f8ce1 has 2 DAI at their disposal.

Step 13: Verify this by checking the Events tab. 🎉

TX2: Simulate the call to approve

The second transaction entails the address 0xe58b9ee93700a616b50509c8292977fa7a0f8ce1 approving 0xf7ddedc66b1d482e5c38e4730b3357d32411e5dd to spend 0.5 DAI.

To run this simulation, follow these steps:

Step 1: Click the New Simulation button.

Step 2: Select the Dai contract from the dropdown.

Step 3: Select the approve function from the function dropdown.

Step 4: Paste the address 0xf7ddedc66b1d482e5c38e4730b3357d32411e5dd to the usr input.

Step 5: Paste the value 500000000000000000 to the wad field.

Step 6: Paste the address 0xe58b9ee93700a616b50509c8292977fa7a0f8ce1 to the from field.

Step 7: Click Simulate.

Step 8. Check the Events tab to verify the Approval event is there. 🎉

TX3: Simulate the call to transferFrom

The last transaction approves the spender (0xf7ddedc66b1d482e5c38e4730b3357d32411e5dd) to transfer 0.25 DAI to 0xbd8daa414fda8a8a129f7035e7496759c5af8570.

Here are the needed steps:

Step 1: Click the New Simulation button.

Step 2: Select the Dai contract from the dropdown.

Step 3: Select the transferFrom function from the function dropdown.

Step 4: Paste the address 0xbd8daa414fda8a8a129f7035e7496759c5af8570 to the usr input.

Step 5: Paste the value 250000000000000000 to the wad field.

Step 6: Paste the spender address (0xf7ddedc66b1d482e5c38e4730b3357d32411e5dd) to the from field.

Step 7: Click Simulate.

Step 8: Check the Events tab to verify that the Approval event is there. 🎉