Another Invariant

.gas-snapshot

@@ -1,15 +1,16 @@
-ModulusFuzz:test_mod_resultIsAlwaysLessThanModDivisor(uint256,uint256) (runs: 256, μ: 38497, ~: 40674)
-GAS_ModulusGas_ModAdmin:test_setModDivisor() (gas: 13835)
+ModulusFuzz:test_mod_resultIsAlwaysLessThanModDivisor(uint256,uint256) (runs: 256, μ: 40853, ~: 43186)
+GAS_ModulusGas_ModAdmin:test_setModDivisor() (gas: 14812)
 GAS_ModulusGas_Owner:test_setModAdmin() (gas: 14155)
 GAS_ModulusGas_Stranger:test_getModDivisor() (gas: 7514)
 GAS_ModulusGas_Stranger:test_getOwner() (gas: 7577)
 GAS_ModulusGas_Stranger:test_getResult() (gas: 7546)
-GAS_ModulusGas_Stranger:test_mod() (gas: 12544)
-ModulusInvariants:invariant_gettersNeverRevert() (runs: 512, calls: 262144, reverts: 0)
+GAS_ModulusGas_Stranger:test_mod() (gas: 14179)
+ModulusInvariants:invariant_gettersNeverRevert() (runs: 256, calls: 65536, reverts: 0)
+ModulusInvariants:invariant_resultShouldAlwaysBeLessThanModDivisor() (runs: 256, calls: 65536, reverts: 0)
 ModulusUnit:test_constructor() (gas: 10608)
-ModulusUnit:test_mod() (gas: 30655)
-ModulusUnit:test_setModAdmin() (gas: 15159)
+ModulusUnit:test_mod() (gas: 36800)
+ModulusUnit:test_setModAdmin() (gas: 20464)
 ModulusUnit:test_setModAdmin_onlyOwner_reverts() (gas: 11986)
-ModulusUnit:test_setModDivisor() (gas: 17968)
+ModulusUnit:test_setModDivisor() (gas: 24647)
 ModulusUnit:test_setModDivisor_onlyModAdmin_reverts() (gas: 11895)
 ModulusUnit:test_setModDivisor_zeroValue_reverts() (gas: 11166)

foundry.toml

@@ -9,8 +9,8 @@ max_test_rejects = 120000
 seed = '0xB00B1E5'
 
 [invariant]
-runs = 512
-depth = 512
+runs = 256
+depth = 256
 fail_on_revert = true
 
 # See more config options https://github.com/foundry-rs/foundry/tree/master/config

src/Modulus.sol

@@ -4,6 +4,7 @@ pragma solidity 0.8.16;
 contract Modulus {
     event ModAdminSet(address indexed previous, address indexed modAdmin);
     event ModDivisorSet(uint256 previous, uint256 modDivisor);
+    event ResultReset();
     event Result(uint256 n, uint256 modDivisor, uint256 result);
 
     error OnlyOwner(address expected, address actual);
@@ -36,10 +37,15 @@ contract Modulus {
         uint256 previous = s_modDivisor;
         s_modDivisor = modDivisor;
         emit ModDivisorSet(previous, modDivisor);
+        s_result = 0;
+        emit ResultReset();
     }
 
     function mod(uint256 n) external {
-        s_result = n % s_modDivisor;
+        uint256 modDivisor = s_modDivisor;
+        uint256 result = n % modDivisor;
+        s_result = result;
+        emit Result(n, modDivisor, result);
     }
 
     function getOwner() external view returns (address owner) {

test/Invariant/Modulus.t.sol → test/Invariant/ModulusInvariants.t.sol

@@ -42,4 +42,8 @@ contract ModulusInvariants is Test, InvariantsBase, Constants {
         s_modulus.getModAdmin();
         s_modulus.getOwner();
     }
+
+    function invariant_resultShouldAlwaysBeLessThanModDivisor() public {
+        assertLe(s_modulus.getResult(), s_modulus.getModDivisor());
+    }
 }

test/Unit/Modulus.t.sol → test/Unit/ModulusUnit.t.sol

@@ -35,7 +35,10 @@ contract ModulusUnit is Test, Constants {
         s_modulus.setModAdmin(STRANGER);
     }
 
+    event ModAdminSet(address indexed previous, address indexed modAdmin);
     function test_setModAdmin() public {
+        vm.expectEmit(true, true, true, false);
+        emit ModAdminSet(s_modulus.getModAdmin(), STRANGER);
         s_modulus.setModAdmin(STRANGER);
         assertEq(s_modulus.getModAdmin(), STRANGER);
     }
@@ -56,20 +59,28 @@ contract ModulusUnit is Test, Constants {
         s_modulus.setModDivisor(0);
     }
 
+    event ModDivisorSet(uint256 previous, uint256 modDivisor);
+    event ResultReset();
     function test_setModDivisor() public {
         changePrank(MOD_ADMIN);
+        vm.expectEmit(true, false, false, false);
+        emit ModDivisorSet(s_modulus.getModDivisor(), MOD_DIVISOR_2);
+        vm.expectEmit(true, false, false, false);
+        emit ResultReset();
         s_modulus.setModDivisor(MOD_DIVISOR_2);
         assertEq(s_modulus.getModDivisor(), MOD_DIVISOR_2);
     }
 
     // ==========================================================================
     // MOD
     // ==========================================================================
-
+    event Result(uint256 n, uint256 modDivisor, uint256 result);
     function test_mod() public {
         uint256 numerator = 50;
         uint256 expected = numerator % MOD_DIVISOR_1;
 
+        vm.expectEmit(true, false, false, false);
+        emit Result(numerator, MOD_DIVISOR_1, expected);
         s_modulus.mod(numerator);
         assertEq(s_modulus.getResult(), expected);
     }