test: add Ethereum Mainnet fork test

feat: add "ALCHEMY_API_KEY" env var
feat: add "ethereum"
ci: delete now-stale "version" param in foundry-toolchain
refactor: delete "ETH_RPC_URL" env var
test: delete console log in "testFuzz_Example"
test: use "assertGt" instead of "assertTrue" for "x > 0" comparison

.env.example

@@ -1,4 +1,4 @@
-ETH_RPC_URL="https://goerli.infura.io/v3/INFURA_API_KEY"
+ALCHEMY_API_KEY="YOUR_ALCHEMY_API_KEY"
 ETHERSCAN_API_KEY="YOUR_ETHERSCAN_API_KEY"
 INFURA_API_KEY="YOUR_INFURA_API_KEY"
 MNEMONIC="YOUR_MNEMONIC"

.github/workflows/ci.yml

@@ -22,8 +22,6 @@ jobs:
 
       - name: "Install Foundry"
         uses: "foundry-rs/foundry-toolchain@v1"
-        with:
-          version: "nightly"
 
       - name: "Install Node.js"
         uses: "actions/setup-node@v3"

foundry.toml

@@ -1,6 +1,7 @@
 # Full reference https://github.com/foundry-rs/foundry/tree/master/config
 
 [etherscan]
+ethereum = { key = "${ETHERSCAN_API_KEY}" }
 goerli = { key = "${ETHERSCAN_API_KEY}" }
 
 [fmt]
@@ -31,5 +32,6 @@ fuzz = { runs = 10_000 }
 verbosity = 4
 
 [rpc_endpoints]
+ethereum="https://eth-mainnet.g.alchemy.com/v2/${ALCHEMY_API_KEY}"
 localhost="http://localhost:8545"
 goerli="https://goerli.infura.io/v3/${INFURA_API_KEY}"

test/Foo.t.sol

@@ -5,6 +5,10 @@ import { PRBTest } from "@prb/test/PRBTest.sol";
 import { console2 } from "forge-std/console2.sol";
 import { StdCheats } from "forge-std/StdCheats.sol";
 
+interface IERC20 {
+    function balanceOf(address account) external view returns (uint256);
+}
+
 /// @dev See the "Writing Tests" section in the Foundry Book if this is your first time with Forge.
 /// https://book.getfoundry.sh/forge/writing-tests
 contract FooTest is PRBTest, StdCheats {
@@ -19,10 +23,24 @@ contract FooTest is PRBTest, StdCheats {
         assertTrue(true);
     }
 
-    /// @dev Test that fuzzes an unsigned integer. Run Forge with `-vvvv` to see console logs.
+    /// @dev Test that fuzzes an unsigned integer.
     function testFuzz_Example(uint256 x) external {
         vm.assume(x != 0);
-        console2.log("x", x);
-        assertTrue(x > 0);
+        assertGt(x, 0);
+    }
+
+    /// @dev Test that runs against a fork of Ethereum Mainnet. You need to set `ALCHEMY_API_KEY` in your environment
+    /// for this test to run - you can get an API key for free at https://alchemy.com.
+    function testFork_Example() external {
+        string memory alchemyApiKey = vm.envOr("ALCHEMY_API_KEY", string(""));
+        if (bytes(alchemyApiKey).length == 0) {
+            return;
+        }
+        vm.createSelectFork({urlOrAlias: "ethereum", blockNumber: 16_428_000});
+        address usdc = 0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48;
+        address holder = 0x7713974908Be4BEd47172370115e8b1219F4A5f0;
+        uint256 actualBalance = IERC20(usdc).balanceOf(holder);
+        uint256 expectedBalance = 196_307_713.810457e6;
+        assertEq(actualBalance, expectedBalance);
     }
 }