vm.assume(collateralAmount != 0) Not Working As Expected

[0xriyadh]

I am currently in the invariant testing portion of the course "Advanced Foundry", doing the "Stablecoin" project. There while creating handlers for redeemCollateral in fuzz or invariant testing @PatrickAlphaC used if condition to discard certain runs. But he also mentioned it could be achieved using vm.assume as well. I am trying to implement that but it's giving me errors I don't understand.

The code that works (this was used in the video):

    function redeemCollateral(uint256 _collateralSeed, uint256 _amountCollateral) public {
        ERC20Mock collateral = _getCollateralFromSeed(_collateralSeed);
        uint256 maxCollateralToRedeem = engine.getCollateralBalanceOfUser(msg.sender, address(collateral));
        _amountCollateral = bound(_amountCollateral, 0, maxCollateralToRedeem);
        if (_amountCollateral == 0) {
            return;
        }

        vm.startPrank(msg.sender);
        engine.redeemCollateral(address(collateral), _amountCollateral);
        vm.stopPrank();
    }

The code that's giving errors:

    function redeemCollateral(uint256 _collateralSeed, uint256 _amountCollateral) public {
        ERC20Mock collateral = _getCollateralFromSeed(_collateralSeed);
        uint256 maxCollateralToRedeem = engine.getCollateralBalanceOfUser(msg.sender, address(collateral));
        _amountCollateral = bound(_amountCollateral, 0, maxCollateralToRedeem);
        // if (_amountCollateral == 0) {
        //     return;
        // }
        vm.assume(_amountCollateral != 0);

        vm.startPrank(msg.sender);
        engine.redeemCollateral(address(collateral), _amountCollateral);
        vm.stopPrank();
    }

Error with full detail:

Ran 1 test for test/fuzz/InvariantsTest.t.sol:InvariantsTest
[FAIL. Reason: FOUNDRY::ASSUME]
        [Sequence]
                sender=0x4E08Dc99A3Fb19E89b543F51dBbE176AfC6c52F5 addr=[test/fuzz/Handler.t.sol:Handler]0x2e234DAe75C793f67A35089C9d99245E1C58470b calldata=failed() args=[]
                sender=0x0000000000000000000000000000000000000376 addr=[test/fuzz/Handler.t.sol:Handler]0x2e234DAe75C793f67A35089C9d99245E1C58470b calldata=depositCollateral(uint256,uint256) args=[0, 278921122950954583493403671619077362421400 [2.789e41]]
                sender=0x0000000000000000000000000000000031e92b82 addr=[test/fuzz/Handler.t.sol:Handler]0x2e234DAe75C793f67A35089C9d99245E1C58470b calldata=redeemCollateral(uint256,uint256) args=[3935, 1868]
 invariant_protocolMustHaveMoreValueThanTotalCollateralSupply() (runs: 1, calls: 3, reverts: 1)
Logs:
  Bound Result 49012822293230851315290756765
  Bound Result 0
  _amountCollateral:  0

Traces:
  [12272059] InvariantsTest::setUp()
    ├─ [4989807] → new DeployDSC@0x5615dEB798BB3E4dFa0139dFa1b3D433Cc23b72f
    │   └─ ← 24809 bytes of code
    ├─ [5807306] DeployDSC::run()
    │   ├─ [3777689] → new HelperConfig@0x104fBc016F4bb334D775a19E8A6510109AC63E00
    │   │   ├─ [0] VM::startBroadcast()
    │   │   │   └─ ← ()
    │   │   ├─ [372455] → new MockV3Aggregator@0x90193C961A926261B756D1E5bb255e67ff9498A1
    │   │   │   └─ ← 1083 bytes of code
    │   │   ├─ [658896] → new ERC20Mock@0xA8452Ec99ce0C64f20701dB7dD3abDb607c00496
    │   │   │   ├─ emit Transfer(from: 0x0000000000000000000000000000000000000000, to: DeployDSC: [0x5615dEB798BB3E4dFa0139dFa1b3D433Cc23b72f], value: 100000000000 [1e11])
    │   │   │   └─ ← 2829 bytes of code
    │   │   ├─ [372455] → new MockV3Aggregator@0xBb2180ebd78ce97360503434eD37fcf4a1Df61c3
    │   │   │   └─ ← 1083 bytes of code
    │   │   ├─ [658896] → new ERC20Mock@0xDB8cFf278adCCF9E9b5da745B44E754fC4EE3C76
    │   │   │   ├─ emit Transfer(from: 0x0000000000000000000000000000000000000000, to: DeployDSC: [0x5615dEB798BB3E4dFa0139dFa1b3D433Cc23b72f], value: 100000000000 [1e11])
    │   │   │   └─ ← 2829 bytes of code
    │   │   ├─ [0] VM::stopBroadcast()
    │   │   │   └─ ← ()
    │   │   └─ ← 7121 bytes of code
    │   ├─ [912] HelperConfig::activeNetworkConfig() [staticcall]
    │   │   └─ ← MockV3Aggregator: [0x90193C961A926261B756D1E5bb255e67ff9498A1], MockV3Aggregator: [0xBb2180ebd78ce97360503434eD37fcf4a1Df61c3], ERC20Mock: [0xA8452Ec99ce0C64f20701dB7dD3abDb607c00496], ERC20Mock: [0xDB8cFf278adCCF9E9b5da745B44E754fC4EE3C76], 77814517325470205911140941194401928579557062014761831930645393041380819009408 [7.781e76]
    │   ├─ [0] VM::startBroadcast(<pk>)
    │   │   └─ ← ()
    │   ├─ [750023] → new DecentralizedStableCoin@0x5FbDB2315678afecb367f032d93F642f64180aa3
    │   │   ├─ emit OwnershipTransferred(previousOwner: 0x0000000000000000000000000000000000000000, newOwner: 0xf39Fd6e51aad88F6F4ce6aB8827279cffFb92266)
    │   │   └─ ← 3402 bytes of code
    │   ├─ [1038652] → new DSCEngine@0xe7f1725E7734CE288F8367e1Bb143E90bb3F0512
    │   │   └─ ← 4510 bytes of code
    │   ├─ [2446] DecentralizedStableCoin::transferOwnership(DSCEngine: [0xe7f1725E7734CE288F8367e1Bb143E90bb3F0512])
    │   │   ├─ emit OwnershipTransferred(previousOwner: 0xf39Fd6e51aad88F6F4ce6aB8827279cffFb92266, newOwner: DSCEngine: [0xe7f1725E7734CE288F8367e1Bb143E90bb3F0512])
    │   │   └─ ← ()
    │   ├─ [0] VM::stopBroadcast()
    │   │   └─ ← ()
    │   └─ ← DecentralizedStableCoin: [0x5FbDB2315678afecb367f032d93F642f64180aa3], DSCEngine: [0xe7f1725E7734CE288F8367e1Bb143E90bb3F0512], HelperConfig: [0x104fBc016F4bb334D775a19E8A6510109AC63E00]
    ├─ [912] HelperConfig::activeNetworkConfig() [staticcall]
    │   └─ ← MockV3Aggregator: [0x90193C961A926261B756D1E5bb255e67ff9498A1], MockV3Aggregator: [0xBb2180ebd78ce97360503434eD37fcf4a1Df61c3], ERC20Mock: [0xA8452Ec99ce0C64f20701dB7dD3abDb607c00496], ERC20Mock: [0xDB8cFf278adCCF9E9b5da745B44E754fC4EE3C76], 77814517325470205911140941194401928579557062014761831930645393041380819009408 [7.781e76]
    ├─ [1202245] → new Handler@0x2e234DAe75C793f67A35089C9d99245E1C58470b
    │   ├─ [1313] DSCEngine::getCollateralTokens() [staticcall]
    │   │   └─ ← [0xA8452Ec99ce0C64f20701dB7dD3abDb607c00496, 0xDB8cFf278adCCF9E9b5da745B44E754fC4EE3C76]
    │   └─ ← 5327 bytes of code
    └─ ← ()

  [6261] Handler::failed()
    ├─ [0] VM::load(VM: [0x7109709ECfa91a80626fF3989D68f67F5b1DD12D], 0x6661696c65640000000000000000000000000000000000000000000000000000)
    │   └─ ← 0x0000000000000000000000000000000000000000000000000000000000000000
    └─ ← false

  [106258] Handler::depositCollateral(0, 278921122950954583493403671619077362421400 [2.789e41])
    ├─ [0] console::log("Bound Result", 49012822293230851315290756765 [4.901e28]) [staticcall]
    │   └─ ← ()
    ├─ [0] VM::startPrank(0x0000000000000000000000000000000000000376)
    │   └─ ← ()
    ├─ [29528] ERC20Mock::mint(0x0000000000000000000000000000000000000376, 49012822293230851315290756765 [4.901e28])
    │   ├─ emit Transfer(from: 0x0000000000000000000000000000000000000000, to: 0x0000000000000000000000000000000000000376, value: 49012822293230851315290756765 [4.901e28])
    │   └─ ← ()
    ├─ [24651] ERC20Mock::approve(DSCEngine: [0xe7f1725E7734CE288F8367e1Bb143E90bb3F0512], 49012822293230851315290756765 [4.901e28])
    │   ├─ emit Approval(owner: 0x0000000000000000000000000000000000000376, spender: DSCEngine: [0xe7f1725E7734CE288F8367e1Bb143E90bb3F0512], value: 49012822293230851315290756765 [4.901e28])
    │   └─ ← true
    ├─ [60327] DSCEngine::depositCollateral(ERC20Mock: [0xA8452Ec99ce0C64f20701dB7dD3abDb607c00496], 49012822293230851315290756765 [4.901e28])
    │   ├─ emit CollateralDeposited(user: 0x0000000000000000000000000000000000000376, token: ERC20Mock: [0xA8452Ec99ce0C64f20701dB7dD3abDb607c00496], amount: 49012822293230851315290756765 [4.901e28])
    │   ├─ [27689] ERC20Mock::transferFrom(0x0000000000000000000000000000000000000376, DSCEngine: [0xe7f1725E7734CE288F8367e1Bb143E90bb3F0512], 49012822293230851315290756765 [4.901e28])
    │   │   ├─ emit Approval(owner: 0x0000000000000000000000000000000000000376, spender: DSCEngine: [0xe7f1725E7734CE288F8367e1Bb143E90bb3F0512], value: 0)
    │   │   ├─ emit Transfer(from: 0x0000000000000000000000000000000000000376, to: DSCEngine: [0xe7f1725E7734CE288F8367e1Bb143E90bb3F0512], value: 49012822293230851315290756765 [4.901e28])
    │   │   └─ ← true
    │   └─ ← ()
    ├─ [0] VM::stopPrank()
    │   └─ ← ()
    └─ ← ()

  [17805] Handler::redeemCollateral(3935, 1868)
    ├─ [2738] DSCEngine::getCollateralBalanceOfUser(0x0000000000000000000000000000000031e92b82, ERC20Mock: [0xDB8cFf278adCCF9E9b5da745B44E754fC4EE3C76]) [staticcall]
    │   └─ ← 0
    ├─ [0] console::log("Bound Result", 0) [staticcall]
    │   └─ ← ()
    ├─ [0] console::log("_amountCollateral: ", 0) [staticcall]
    │   └─ ← ()
    ├─ [0] VM::assume(false) [staticcall]
    │   └─ ← FOUNDRY::ASSUME
    └─ ← FOUNDRY::ASSUME

Test result: FAILED. 0 passed; 1 failed; 0 skipped; finished in 18.60ms

Ran 1 test suite in 18.60ms: 0 tests passed, 1 failed, 0 skipped (1 total tests)

Failing tests:
Encountered 1 failing test in test/fuzz/InvariantsTest.t.sol:InvariantsTest
[FAIL. Reason: FOUNDRY::ASSUME]
        [Sequence]
                sender=0x4E08Dc99A3Fb19E89b543F51dBbE176AfC6c52F5 addr=[test/fuzz/Handler.t.sol:Handler]0x2e234DAe75C793f67A35089C9d99245E1C58470b calldata=failed() args=[]
                sender=0x0000000000000000000000000000000000000376 addr=[test/fuzz/Handler.t.sol:Handler]0x2e234DAe75C793f67A35089C9d99245E1C58470b calldata=depositCollateral(uint256,uint256) args=[0, 278921122950954583493403671619077362421400 [2.789e41]]
                sender=0x0000000000000000000000000000000031e92b82 addr=[test/fuzz/Handler.t.sol:Handler]0x2e234DAe75C793f67A35089C9d99245E1C58470b calldata=redeemCollateral(uint256,uint256) args=[3935, 1868]
 invariant_protocolMustHaveMoreValueThanTotalCollateralSupply() (runs: 1, calls: 3, reverts: 1)

Encountered a total of 1 failing tests, 0 tests succeeded

[EngrPips]

Hello @mahadihassanriyadh, I must confess that I didn't implement the vm.assume in my codebase while taking the course as I don't have enough time on my hand to read the Foundry docs in case I run into any issue as you did now. I suggest you look into the Foundry Book to see what has changed and why it might fail: https://book.getfoundry.sh/cheatcodes/?highlight=vm.assume#cheatcodes-reference .

[0xriyadh]

Hi, @EngrPips I have already looked through the docs. But I am not able to understand why vm.assume is not working as stated in the docs for my scenario. With if statement the tests work completely fine but not for vm.assume. Thank you for your support, I really appreciate it. I will look more into it.

[EngrPips]

Yeah, the if statement works fine for me, too, so I never tried the vm.assume. I would like to know whatever you find out.

[PatrickAlphaC]

So vm.assume(_amountCollateral != 0); is sort of "dumb" with how it works with fuzz runs. In the video, that was actually a bit of a mistake of mine.

vm.assume(); will blindly toss the run if it sees a condition that is not satisfied, and essentially reverts. Since we have set fail_on_revert to true, this means that anytime vm.assume() hits a condition that evaluates to false the run is considered failed.

Does that make sense?

[EngrPips]

Yeah, Makes sense sir. Thanks for the clarification sir.

[0xriyadh]

Yeah, that makes perfect sense. Thank you.