Add foundry for invariant testing

.gitmodules

@@ -0,0 +1,3 @@
+[submodule "lib/forge-std"]
+	path = lib/forge-std
+	url = https://github.com/foundry-rs/forge-std

foundry.toml

@@ -0,0 +1,15 @@
+[profile.default]
+src = 'contracts'
+out = 'out'
+libs = ['node_modules', 'lib']
+test = 'test'
+cache_path  = 'cache_forge'
+solc = '0.8.18'
+
+[fuzz]
+runs = 1_000
+depth = 100
+
+# Extreme Fuzzing CI Profile
+[profile.ci]
+runs = 100_000

hardhat.config.ts

@@ -1,6 +1,7 @@
 import { HardhatUserConfig } from 'hardhat/config';
 import '@nomicfoundation/hardhat-toolbox';
 import '@nomicfoundation/hardhat-chai-matchers';
+import "@nomicfoundation/hardhat-foundry";
 import '@openzeppelin/hardhat-upgrades';
 import dotenv from 'dotenv';
 

package.json

@@ -20,13 +20,14 @@
     "url": "git+https://github.com/mountainprotocol/tokens.git"
   },
   "author": "Mati <mattiascaricato@gmail.com>",
-  "license": "UNLICENSED",
+  "license": "MIT",
   "bugs": {
     "url": "https://github.com/mountainprotocol/tokens/issues"
   },
   "homepage": "https://github.com/mountainprotocol/tokens#readme",
   "devDependencies": {
     "@nomicfoundation/hardhat-chai-matchers": "^1.0.6",
+    "@nomicfoundation/hardhat-foundry": "^1.0.1",
     "@nomicfoundation/hardhat-toolbox": "^2.0.1",
     "@openzeppelin/hardhat-upgrades": "^1.22.1",
     "@openzeppelin/test-helpers": "^0.5.16",

remappings.txt

@@ -0,0 +1,7 @@
+@ensdomains/=node_modules/@ensdomains/
+@openzeppelin/contracts/=node_modules/@openzeppelin/contracts/
+@openzeppelin/contracts-upgradeable/=node_modules/@openzeppelin/contracts-upgradeable/
+ds-test/=lib/forge-std/lib/ds-test/src/
+eth-gas-reporter/=node_modules/eth-gas-reporter/
+forge-std/=lib/forge-std/src/
+hardhat/=node_modules/hardhat/

test/USDMTest.t.sol

@@ -0,0 +1,59 @@
+// SPDX-License-Identifier: MIT
+pragma solidity 0.8.18;
+
+import {Test} from "forge-std/Test.sol";
+import {console} from "forge-std/console.sol";
+import {ERC1967Proxy} from "@openzeppelin/contracts/proxy/ERC1967/ERC1967Proxy.sol";
+
+import "../contracts/USDM.sol";
+
+contract UUPSProxy is ERC1967Proxy {
+    constructor(address _implementation, bytes memory _data)
+        ERC1967Proxy(_implementation, _data)
+    {}
+}
+
+contract Handler {
+    USDM public usdm;
+
+    constructor(USDM _usdm) {
+        usdm = _usdm;
+    }
+}
+
+contract USDMInvariants is Test {
+    USDM implementation;
+    UUPSProxy proxy;
+    USDM usdm;
+    Handler handler;
+
+    function setUp() public {
+        // deploy implementation contract
+        implementation = new USDM();
+
+        // deploy proxy contract and point it to implementation
+        proxy = new UUPSProxy(address(implementation), "");
+
+        // wrap in ABI to support easier calls
+        usdm = USDM(address(proxy));
+
+        usdm.initialize("Mountain Protocol USD", "USDM", 0);
+
+        handler = new Handler(usdm);
+
+        // targetContract(address(handler));
+        // targetContract(address(implementation));
+    }
+
+    function invariant_totalSupply() public {
+        assertEq(usdm.balanceOf(address(this)), usdm.totalSupply());
+    }
+
+    function invariant_totalShares() public {
+        assertEq(usdm.sharesOf(address(this)), usdm.totalShares());
+    }
+
+    function invariant_totalShares_totalSupply() public {
+        assertEq(usdm.totalSupply(), usdm.totalShares());
+    }
+}