Merge pull request #342 from reytchison/reytchison-patch

Update Echidna exercise pages and small fixes

Author: montyly

program-analysis/echidna/advanced/smart-contract-fuzzing-at-scale.md

@@ -74,7 +74,7 @@ Once it runs, check the coverage file located in `corpus-exploration/covered.*.t
 
 ## 3. Initiate a continuous fuzzing campaign
 
-When satisfied with the first iteration of the initialization, we can start a "continuous campaign" for exploration and testing using [echidna-parade](https://github.com/agroce/echidna-parade). Before starting, double-check your config file. For instance, if you added properties, do not forget to remove `benchmarkMode`.
+When satisfied with the first iteration of the initialization, we can start a "continuous campaign" for exploration and testing using [echidna-parade](https://github.com/crytic/echidna-parade). Before starting, double-check your config file. For instance, if you added properties, do not forget to remove `benchmarkMode`.
 
 `echidna-parade` is a tool used to launch multiple Echidna instances simultaneously while keeping track of each corpus. Each instance will be configured to run for a specific duration, with different parameters, to maximize the chance of reaching new code.
 

program-analysis/echidna/basic/working-with-eth.md

@@ -116,4 +116,4 @@ echidna_C_has_some_value: failed!💥
 Echidna has two options for using ether during a fuzzing campaign.
 
 - `maxValue` to set the max amount of ether per transaction
-- `contractBalance` to set the initial amount of ether that the testing contract receives in the constructor.
+- `balanceContract` to set the initial amount of ether that the testing contract receives in the constructor.

program-analysis/echidna/exercises/Exercise-1.md

@@ -51,8 +51,11 @@ contract Token is Ownable, Pausable {
     mapping(address => uint256) public balances;
 
     function transfer(address to, uint256 value) public whenNotPaused {
-        balances[msg.sender] -= value;
-        balances[to] += value;
+        // unchecked to save gas
+        unchecked {
+            balances[msg.sender] -= value;
+            balances[to] += value;
+        }
     }
 }
 ```
@@ -79,8 +82,8 @@ import "./token.sol";
 contract TestToken is Token {
     address echidna = tx.origin;
 
-    constructor() public {
-        balances[echidna] = 10000;
+    constructor() {
+        balances[echidna] = 10_000;
     }
 
     function echidna_test_balance() public view returns (bool) {

program-analysis/echidna/exercises/Exercise-2.md

@@ -84,7 +84,7 @@ import "./token.sol";
 ///      echidna program-analysis/echidna/exercises/exercise2/template.sol
 ///      ```
 contract TestToken is Token {
-    constructor() public {
+    constructor() {
         pause(); // pause the contract
         owner = address(0); // lose ownership
     }

program-analysis/echidna/exercises/Exercise-3.md

@@ -19,7 +19,7 @@ We will test the following contract _[token.sol](https://github.com/crytic/build
 ```solidity
 pragma solidity ^0.8.0;
 
-/// @notice The issues from exercises 1 and 2 are fixed.
+/// @notice The issues from exercise 1 and 2 are fixed.
 
 contract Ownable {
     address public owner = msg.sender;
@@ -74,7 +74,7 @@ contract MintableToken is Token {
     int256 public totalMinted;
     int256 public totalMintable;
 
-    constructor(int256 totalMintable_) public {
+    constructor(int256 totalMintable_) {
         totalMintable = totalMintable_;
     }
 
@@ -111,7 +111,7 @@ contract TestToken is MintableToken {
     address echidna = msg.sender;
 
     // TODO: update the constructor
-    constructor(int256 totalMintable) public MintableToken(totalMintable) {}
+    constructor(int256 totalMintable) MintableToken(totalMintable) {}
 
     function echidna_test_balance() public view returns (bool) {
         // TODO: add the property

program-analysis/echidna/exercises/Exercise-4.md

@@ -27,7 +27,7 @@ contract Ownable {
     }
 
     modifier onlyOwner() {
-        require(msg.sender == owner, "Ownable: Caller is not the owner");
+        require(msg.sender == owner, "Ownable: Caller is not the owner.");
         _;
     }
 }
@@ -48,17 +48,20 @@ contract Pausable is Ownable {
     }
 
     modifier whenNotPaused() {
-        require(!_paused, "Pausable: Contract is paused");
+        require(!_paused, "Pausable: Contract is paused.");
         _;
     }
 }
 
 contract Token is Ownable, Pausable {
     mapping(address => uint256) public balances;
 
-    function transfer(address to, uint256 value) public whenNotPaused {
-        balances[msg.sender] -= value;
-        balances[to] += value;
+    function transfer(address to, uint256 value) public virtual whenNotPaused {
+        // unchecked to save gas
+        unchecked {
+            balances[msg.sender] -= value;
+            balances[to] += value;
+        }
     }
 }
 ```
@@ -88,6 +91,10 @@ import "./token.sol";
 ///      solc-select use 0.8.0
 ///      echidna program-analysis/echidna/exercises/exercise4/template.sol --contract TestToken --test-mode assertion
 ///      ```
+///      or by providing a config
+///      ```
+///      echidna program-analysis/echidna/exercises/exercise4/template.sol --contract TestToken --config program-analysis/echidna/exercises/exercise4/config.yaml
+///      ```
 contract TestToken is Token {
     function transfer(address to, uint256 value) public {
         // TODO: include `assert(condition)` statements that