Cli Forge

Foundry Testing & Script Skill

Rules and patterns for Foundry tests. Find examples in the actual codebase.

Bundled References

| Reference | Content | When to Read | | -------------------------------------- | ------------------------------ | ------------------------------ | | ./references/test-infrastructure.md | Constants, defaults, mocks | When setting up tests | | ./references/cheat-codes.md | Common cheatcode patterns | When using vm cheatcodes | | ./references/invariant-patterns.md | Handlers, stores, invariants | When writing invariant tests | | ./references/formal-verification.md | Halmos, Certora, symbolic exec | When proving correctness | | ./references/deployment-scripts.md | Script patterns, verification | When writing deploy scripts | | ./references/deployment-checklist.md | Pre-mainnet deployment steps | Before deploying to production | | ./references/gas-benchmarking.md | Snapshot, profiling, CI | When measuring gas performance | | ./references/sablier-conventions.md | Sablier-specific patterns | When working in Sablier repos |

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Test Types

| Type | Directory | Naming | Purpose | | ----------- | ----------------------------- | ------------------ | ---------------------------- | | Integration | tests/integration/concrete/ | *.t.sol | BTT-based concrete tests | | Fuzz | tests/integration/fuzz/ | *.t.sol | Property-based testing | | Fork | tests/fork/ | *.t.sol | Mainnet state testing | | Invariant | tests/invariant/ | Invariant*.t.sol | Stateful protocol properties | | Scripts | scripts/solidity/ | *.s.sol | Deployment/initialization |

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1. Integration Tests (Concrete)

Naming Convention

| Pattern | Usage | | ----------------------------- | --------------- | | test_RevertWhen_{Condition} | Revert on input | | test_RevertGiven_{State} | Revert on state | | test_When_{Condition} | Success path |

Rules

1. Stack modifiers to document BTT path (modifiers are often empty - just document the path)
2. Expect events BEFORE action - vm.expectEmit() then call function
3. Assert state AFTER action - Check state changes after function executes
4. Use revert helpers for common patterns (expectRevert_DelegateCall, expectRevert_Null)
5. Named parameters in assertions - assertEq(actual, expected, "description")

Mock Rules

1. Place all mocks in tests/mocks/
2. One mock per scenario (not one mega-mock)
3. Naming: *Good, *Reverting, *InvalidSelector, *Reentrant

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2. Fuzz Tests

Naming Convention

testFuzz_{FunctionName}_{Scenario}

Rules

1. Bound before assume - _bound() is more efficient than vm.assume()
2. Bound in dependency order - Independent params first, then dependent
3. Never hardcode params with validation constraints
4. Document fuzzed scenarios in NatSpec

Bounding Pattern

// 1. Bound independent params first
cliffDuration = boundUint40(cliffDuration, 0, MAX - 1);

// 2. Bound dependent params based on constraints
totalDuration = boundUint40(totalDuration, cliffDuration + 1, MAX);

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3. Fork Tests

Rules

1. Create fork with vm.createSelectFork("ethereum")
2. Use deal() to give tokens to test users
3. Use assumeNoBlacklisted() for USDC/USDT
4. Use forceApprove() for non-standard tokens (USDT)

Token Quirks

| Token | Issue | Solution | | --------------- | ------------ | ---------------------------- | | USDC/USDT | Blacklist | assumeNoBlacklisted() | | USDT | Non-standard | forceApprove() | | Fee-on-transfer | Balance diff | Check actual received amount |

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4. Invariant Tests

Architecture

tests/invariant/
├── handlers/     # State manipulation (call functions with bounded params)
├── stores/       # State tracking (record totals, IDs)
└── Invariant.t.sol

Rules

1. Target handlers only - targetContract(address(handler))
2. Exclude protocol contracts - excludeSender(address(vault))
3. Use stores to track totals for invariant assertions
4. Early return in handlers if preconditions not met

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5. Solidity Scripts

Rules

1. Inherit from BaseScript with broadcast modifier
2. Use env vars: ETH_FROM, MNEMONIC
3. Simulation first, then broadcast

Commands

# Simulation
forge script scripts/Deploy.s.sol --sig "run(...)" ARGS --rpc-url $RPC

# Broadcast
forge script scripts/Deploy.s.sol --sig "run(...)" ARGS --rpc-url $RPC --broadcast --verify

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Running Tests

# By type
forge test --match-path "tests/integration/concrete/**"
forge test --match-path "tests/fork/**"
forge test --match-contract Invariant_Test

# Specific test
forge test --match-test test_WhenCallerRecipient -vvvv

# Fuzz with more runs
forge test --match-test testFuzz_ --fuzz-runs 1000

# Coverage
forge coverage --report lcov

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Debugging

Verbosity Levels

| Flag | Shows | | -------- | --------------------------- | | -v | Logs for failing tests | | -vv | Logs for all tests | | -vvv | Stack traces for failures | | -vvvv | Stack traces + setup traces | | -vvvvv | Full execution traces |

Console Logging

import { console2 } from "forge-std/console2.sol";

console2.log("value:", someValue);
console2.log("address:", someAddress);
console2.logBytes32(someBytes32);

Debugging Commands

# Trace specific failing test
forge test --match-test test_MyTest -vvvv

# Gas report for a test
forge test --match-test test_MyTest --gas-report

# Debug in interactive debugger
forge debug --debug tests/MyTest.t.sol --sig "test_MyTest()"

# Inspect storage layout
forge inspect MyContract storage-layout

Debugging Tips

1. Label addresses - vm.label(addr, "Recipient") for readable traces
2. Check state with logs - Add console2.log before reverts
3. Isolate failures - Run single test with --match-test
4. Compare gas - Use --gas-report to spot unexpected costs
5. Snapshot comparisons - Use vm.snapshot() / vm.revertTo() to isolate state changes

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Best Practices Summary

1. Use constants from Defaults/Constants - never hardcode
2. Specialized mocks - one per scenario, all in tests/mocks/
3. Modifiers in Modifiers.sol - centralize BTT path modifiers
4. Label addresses with vm.label() for traces
5. Events before actions - vm.expectEmit() then call
6. Bound before assume - more efficient

External References

• Foundry Book

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Example Invocations

Test this skill with these prompts:

1. Integration test: "Write a concrete test for withdraw that expects Errors.Flow_Overdraw when amount exceeds

balance"

1. Fuzz test: "Create a fuzz test for deposit that bounds amount between 1 and type(uint128).max"
2. Fork test: "Write a fork test for USDC deposits on mainnet with blacklist handling"
3. Invariant test: "Create an invariant handler for the deposit and withdraw functions"
4. Deploy script: "Write a deployment script for SablierFlow with verification"

Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

• Author: sablier-labs
• Source: sablier-labs/agent-skills
• License: MIT

Install and usage instructions live in the source repository linked above.