Fork testing (mainnet fork) in Blockchain / Solidity - Step-by-Step Execution

Concept Flow - Fork testing (mainnet fork)

Start Mainnet Fork Setup

↓

Clone Mainnet State

↓

Deploy Forked Chain Locally

↓

Run Tests on Forked Chain

↓

Analyze Test Results

↓

Decide: Fix or Deploy

↓

Fix

This flow shows how a mainnet fork is created locally to test changes safely before deciding to fix issues or deploy.

Execution Sample

Blockchain / Solidity

1. fork = createMainnetFork(rpcUrl)
2. deployContracts(fork)
3. runTests(fork)
4. analyzeResults()
5. decideNextStep()

This code creates a mainnet fork, deploys contracts, runs tests, analyzes results, and decides next steps.

Execution Table

Step	Action	Input/Condition	Result/Output
1	Create mainnet fork	RPC URL to mainnet node	Forked chain state cloned locally
2	Deploy contracts	Forked chain instance	Contracts deployed on fork
3	Run tests	Deployed contracts on fork	Test results collected
4	Analyze results	Test results	Identify pass/fail and issues
5	Decide next step	Analysis outcome	Choose to fix or deploy
6	Exit	Decision made	End of fork testing process

💡 Testing ends after decision to fix issues or deploy changes

Variable Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	After Step 4	Final
fork	null	forked chain instance	forked chain instance	forked chain instance	forked chain instance	forked chain instance
contractsDeployed	false	false	true	true	true	true
testResults	null	null	null	results object	results object	results object
decision	null	null	null	null	null	fix or deploy

Key Moments - 3 Insights

Why do we clone the mainnet state instead of testing directly on mainnet?

Cloning mainnet state creates a safe local copy to test without risking real assets or affecting live users, as shown in step 1 of the execution_table.

What happens if tests fail on the forked chain?

If tests fail (step 4), the decision (step 5) is usually to fix issues before deploying, preventing broken code on mainnet.

Is the forked chain connected to the real mainnet after creation?

No, after cloning, the forked chain runs locally and independently, allowing isolated testing as indicated by the 'forked chain instance' variable state.

Visual Quiz - 3 Questions

Look at the execution_table, what is the output after step 2?

A Test results collected

B Contracts deployed on fork

C Forked chain state cloned locally

D Identify pass/fail and issues

💡 Hint

Check the 'Result/Output' column for step 2 in the execution_table.

At which step do we analyze the test results?

A Step 3

B Step 5

C Step 4

D Step 1

💡 Hint

Look for the action 'Analyze results' in the execution_table.

If the fork variable was null after step 1, what would that mean?

A Fork creation failed

B Contracts deployed successfully

C Tests passed

D Decision made to deploy

💡 Hint

Refer to variable_tracker for 'fork' variable state after step 1.

Concept Snapshot

Fork testing (mainnet fork):
- Clone mainnet state locally
- Deploy contracts on fork
- Run tests safely
- Analyze results
- Decide to fix or deploy
- Ensures safe testing without risking mainnet

Full Transcript

Fork testing with a mainnet fork means creating a local copy of the mainnet blockchain state. This lets developers test their code safely without affecting the real network. The process starts by cloning the mainnet state using an RPC URL. Then contracts are deployed on this forked chain. Tests run on the fork collect results, which are analyzed to find any issues. Based on the analysis, developers decide whether to fix problems or deploy the code. This approach protects real assets and users by isolating testing from the live mainnet.