FundMeTest.t.sol test cheatcodes lesson7.13

[Hamobcdev]

Hi i am having trouble figuring out why this test passes when it doesn't in the video,

function testFailsWithoutEnoughETH() public {
        vm.expectRevert(); // hey, the next line, should revert.
        // assert(this tx Fail/reverts)
        uint256 cat = 1; 
    }
    ```
and i get this pass output:

foundry-fund-me$ forge test --mt testFailsWithoutEnoughETH
[⠒] Compiling...
[⠊] Compiling 1 files with Solc 0.8.19
[⠒] Solc 0.8.19 finished in 1.80s
Compiler run successful with warnings:
Warning (2072): Unused local variable.
--> test/FundMeTest.t.sol:34:9:
|
34 | uint256 cat = 1;
| ^^^^^^^^^^^

Ran 1 test for test/FundMeTest.t.sol:FundMeTest
[PASS] testFailsWithoutEnoughETH() (gas: 3068)
Suite result: ok. 1 passed; 0 failed; 0 skipped; finished in 893.68µs (53.47µs CPU time)

Ran 1 test suite in 20.89ms (893.68µs CPU time): 1 tests passed, 0 failed, 0 skipped (1 total tests)

however when i change the code to the next step adding 

function testFailsWithoutEnoughETH() public {
vm.expectRevert(); // hey, the next line, should revert.
// assert(this tx Fail/reverts)
fundMe.fund(); //send 0 value
}
```
I get the fail error expected in the first step?

forge test --mt testFailsWithoutEnoughETH
[⠒] Compiling...
[⠊] Compiling 1 files with Solc 0.8.19
[⠒] Solc 0.8.19 finished in 1.83s
Compiler run successful!

Ran 1 test for test/FundMeTest.t.sol:FundMeTest
[FAIL. Reason: assertion failed] testFailsWithoutEnoughETH() (gas: 22995)
Suite result: FAILED. 0 passed; 1 failed; 0 skipped; finished in 1.00ms (135.37µs CPU time)

Ran 1 test suite in 20.81ms (1.00ms CPU time): 0 tests passed, 1 failed, 0 skipped (1 total tests)

Failing tests:
Encountered 1 failing test in test/FundMeTest.t.sol:FundMeTest
[FAIL. Reason: assertion failed] testFailsWithoutEnoughETH() (gas: 22995)

Encountered a total of 1 failing tests, 0 tests succeeded

tried looking for an answer unsuccessfully would really appreciate a hand with this, please, thanks.

// SPDX-License-Identifier: MIT

pragma solidity ^0.8.18;

import {Test, console} from "forge-std/Test.sol";
import {FundMe} from "../src/FundMe.sol";
import {DeployFundMe} from "../script/DeployFundMe.s.sol";

contract FundMeTest is Test {
    FundMe fundMe;

    function setUp() external {
        //fundMe = new FundMe(0x694AA1769357215DE4FAC081bf1f309aDC325306);
        DeployFundMe deployFundMe = new DeployFundMe();
        fundMe = deployFundMe.run();
    }

    function testMinimumDollarIsFive() public view {
        assertEq(fundMe.MINIMUM_USD(), 5e18);
    }

    function testOwnerIsMsgSender() public view {
        assertEq(fundMe.i_owner(), msg.sender);
    }

    function testPriceFeedVersionIsAccurate() public view {
        uint256 version = fundMe.getVersion();
        assertEq(version, 4);
    }

    function testFailsWithoutEnoughETH() public {
        vm.expectRevert(); // hey, the next line, should revert.
        // assert(this tx Fail/reverts)
        fundMe.fund(); //send 0 value
    }
}
``` for added context full FundMeTest.t.sol cheers

[EngrPips]

Hello @Hamobcdev, Foundry now has a feature where if you name a test function with the Fail word in it, such as testFailWithoutEnoughETH, the test will only pass if it reverts, and it will fail if it doesn't revert. You can read more about this here: https://book.getfoundry.sh/forge/writing-tests?highlight=TestFails#writing-tests.

So, let's understand why your test function seems to be behaving abnormally.

** TEST 1 **
You name the test below as testFailsWithoutEnoughETH, so this would make it so the test would only pass if it reverted. But then, inside the function, you have this line of code: vm.expectRevert() [This line of code declares that the next line of code should revert]. That makes it so the test function has two revert commands, which will cancel out each other, and then the test will return to its normal behavior.

function testFailsWithoutEnoughETH() public {
        vm.expectRevert(); // hey, the next line should revert.
        // assert(this tx Fail/reverts)
        uint256 cat = 1; 
    }

So the main point is that if you already name a test function with a Fail keyword following the test keyword, you don't need this line of code, vm.expectRevert(), in the test function, as it will only negate the expected behavior. To prove this, I ran my test without the vm.expectRevert() line of code, and it behaved as I expected. Below is the test code and output.

TEST CODE

 function testFailsWithoutEnoughETH1() public {
        // vm.expectRevert(); // hey, the next line, should revert.
        // assert(this tx Fail/reverts)
        uint256 cat = 1; 
      
    }

TEST OUTPUT

Ran 1 test for test/unit/FundMeTest.t.sol:FundMeTest
[FAIL. Reason: assertion failed] testFailsWithoutEnoughETH1() (gas: 143)
Traces:
  [2440785] FundMeTest::setUp()
    ├─ [1057798] → new DeployFundMe@0x5615dEB798BB3E4dFa0139dFa1b3D433Cc23b72f
    │   └─ ← [Return] 5173 bytes of code
    ├─ [1300315] DeployFundMe::run()
    │   ├─ [427567] → new HelperConfig@0x104fBc016F4bb334D775a19E8A6510109AC63E00
    │   │   └─ ← [Return] 2025 bytes of code
    │   ├─ [413423] HelperConfig::getAnvilNetworkConfig()
    │   │   ├─ [0] VM::startBroadcast()
    │   │   │   └─ ← [Return] 
    │   │   ├─ [377461] → new MockV3Aggregator@0x90193C961A926261B756D1E5bb255e67ff9498A1
    │   │   │   └─ ← [Return] 1108 bytes of code
    │   │   ├─ [0] VM::stopBroadcast()
    │   │   │   └─ ← [Return] 
    │   │   └─ ← [Return] MockV3Aggregator: [0x90193C961A926261B756D1E5bb255e67ff9498A1]
    │   ├─ [0] VM::startBroadcast()
    │   │   └─ ← [Return] 
    │   ├─ [370298] → new FundMe@0xA8452Ec99ce0C64f20701dB7dD3abDb607c00496
    │   │   └─ ← [Return] 1848 bytes of code
    │   ├─ [0] VM::stopBroadcast()
    │   │   └─ ← [Return] 
    │   └─ ← [Return] FundMe: [0xA8452Ec99ce0C64f20701dB7dD3abDb607c00496]
    ├─ [0] VM::deal(Owner: [0x93B07479cC807d037A98B6bB122CE8201958a595], 100000000000000000000 [1e20])
    │   └─ ← [Return] 
    └─ ← [Stop] 

  [143] FundMeTest::testFailsWithoutEnoughETH1()
    └─ ← [Stop] 

Suite result: FAILED. 0 passed; 1 failed; 0 skipped; finished in 13.19ms (135.46µs CPU time)

Ran 1 test suite in 1.75s (13.19ms CPU time): 0 tests passed, 1 failed, 0 skipped (1 total tests)

Failing tests:
Encountered 1 failing test in test/unit/FundMeTest.t.sol:FundMeTest
[FAIL. Reason: assertion failed] testFailsWithoutEnoughETH1() (gas: 143)

TEST 2
The same thing applied to your second test below

function testFailsWithoutEnoughETH() public {
vm.expectRevert(); // hey, the next line should revert.
// assert(this tx Fail/reverts)
fundMe.fund(); //send 0 value
}

I ran the test excluding the vm.expectRevert() line of code, and it behaves as I have expected; below is my test code and test output

TEST CODE

function testFailsWithoutEnoughETH() public {
        // vm.expectRevert(); // hey, the next line, should revert.
        // // assert(this tx Fail/reverts)
        fundMe.fund(); //send 0 value
    }

TEST OUTPUT

Ran 1 test for test/unit/FundMeTest.t.sol:FundMeTest
[PASS] testFailsWithoutEnoughETH() (gas: 17952)
Traces:
  [17952] FundMeTest::testFailsWithoutEnoughETH()
    ├─ [12710] FundMe::fund()
    │   ├─ [8993] MockV3Aggregator::latestRoundData() [staticcall]
    │   │   └─ ← [Return] 1, 100000000000 [1e11], 1, 1, 1
    │   └─ ← [Revert] revert: You didn't send enough ether
    └─ ← [Revert] revert: You didn't send enough ether

Suite result: ok. 1 passed; 0 failed; 0 skipped; finished in 15.72ms (444.61µs CPU time)

Please let us know if you still need clarification.

[Hamobcdev]

thanks very much for the help @EngrPips, that worked, I understand what you are saying but wonder why it was different in the tutorial, I will read up more on the usage of the revert commands. most appreciated and thank you.

[Hamobcdev]

'Fail "being a "Key word" so i should possibly try it without the fail in it, and yes the word fails exchanged for Stops works, interesting, thank you very much.

[EngrPips]

Anytime, Friend. I am glad I could help. You can mark the discussion as answered.

[Hamobcdev]

got sort off stuck on this again with the vm.revert statement and test kept failing, just needed to comment out the vm.revert, luckily had this to come back to and all 9 test passed, thanks again.

[EngrPips]

Awesome. Keep crushing it buddy.

[wilson0922]

You guys saved me, too! Thank you so much!!

[EngrPips]

You are welcome, Friend. We are happy this discussion helped you unblock yourself. Keep crushing it