Add external oracle tester contract test

protocol/contracts/libraries/Oracle/LibUsdOracle.sol

@@ -168,8 +168,15 @@ library LibUsdOracle {
         // Non-zero addresses are enforced in verifyOracleImplementation, this is just an extra check.
         if (oracleImpl.target == address(0)) return 0;
 
+        // if `isMillion` is enabled, append the boolean into the oracleImpl,
+        // such that the oracle implementation can use the data.
+        bytes memory oracleImplData = oracleImpl.data;
+        if (isMillion) {
+            oracleImplData = abi.encodePacked(oracleImpl.data, isMillion);
+        }
+
         (bool success, bytes memory data) = oracleImpl.target.staticcall(
-            abi.encodeWithSelector(oracleImpl.selector, tokenDecimals, lookback, oracleImpl.data)
+            abi.encodeWithSelector(oracleImpl.selector, tokenDecimals, lookback, oracleImplData)
         );
 
         if (!success) return 0;

protocol/foundry.toml

@@ -6,10 +6,7 @@ test = 'test'
 script = 'script'
 no_match_test = "testDiff"
 out = 'out'
-libs = [
-  'node_modules',
-  'lib'
-]
+libs = ['node_modules', 'lib']
 cache = true
 cache_path = 'cache'
 force = false
@@ -34,18 +31,19 @@ bytecode_hash = 'ipfs'
 verbosity = 0
 ffi = true
 fs_permissions = [
-  { access = "read", path = "../"},
-  { access = "read", path = "./out" }
+  { access = "read", path = "../" },
+  { access = "read", path = "./out" },
 ]
 ignored_warnings_from = [
   "test",
   "contracts/interfaces/IMockFBeanstalk.sol",
-  "contracts/mocks/"
+  "contracts/mocks/",
 ]
 gas_reports = ['*']
- # Cache to `$HOME/.foundry/cache/<chain id>/<block number>`.
+# Cache to `$HOME/.foundry/cache/<chain id>/<block number>`.
 no_storage_caching = false
-
+no_match_contract = "ReseedStateTest"
+
 [profile.differential]
 match_test = "testDiff"
 no_match_test = "a^"
@@ -55,9 +53,9 @@ chains = 'all'
 endpoints = 'all'
 
 [rpc_endpoints]
-mainnet = "${FORKING_RPC}" 
+mainnet = "${FORKING_RPC}"
 
 [invariant]
 runs = 4
 depth = 2048
-fail_on_revert = true
+fail_on_revert = true

protocol/test/foundry/silo/Oracle.t.sol

@@ -195,6 +195,28 @@ contract OracleTest is TestHelper {
         assertEq(xEthTimeout, _xEthTimeout);
     }
 
+    function testExternalOracleImplementation() public {
+        // setup oracle implementation
+        address oracle = address(new ExternalOracleTester());
+        vm.prank(BEANSTALK);
+        bs.updateOracleImplementationForToken(
+            WBTC,
+            IMockFBeanstalk.Implementation(
+                oracle,
+                ExternalOracleTester.getPrice.selector,
+                bytes1(0x00), // 0x00 is external
+                abi.encode(LibChainlinkOracle.FOUR_HOUR_TIMEOUT)
+            )
+        );
+
+        uint256 tokenPriceWBTC = OracleFacet(BEANSTALK).getTokenUsdPrice(WBTC); // should be 50000e6
+        assertEq(tokenPriceWBTC, 50000e6, "getTokenUsdPrice wbtc");
+
+        // also exercise getMillionUsdPrice
+        uint256 tokenPriceWBTCMillion = OracleFacet(BEANSTALK).getMillionUsdPrice(WBTC, 0);
+        assertEq(tokenPriceWBTCMillion, 50000e12, "getMillionUsdPrice wbtc");
+    }
+
     function testGetOracleImplementationForToken() public {
         vm.prank(BEANSTALK);
         bs.updateOracleImplementationForToken(
@@ -422,3 +444,29 @@ contract OracleTest is TestHelper {
         );
     }
 }
+
+contract ExternalOracleTester {
+    function getPrice(
+        uint256 tokenDecimals,
+        uint256 lookback,
+        bytes memory data
+    ) external view returns (uint256) {
+        uint256 timeout;
+        bool isMillion = false;
+
+        if (data.length > 32) {
+            assembly {
+                timeout := mload(add(data, 32))
+                isMillion := byte(0, mload(add(data, 64)))
+            }
+        } else if (data.length == 32) {
+            // only timeout supplied
+            (timeout) = abi.decode(data, (uint256));
+        }
+
+        if (isMillion) {
+            return 50000e12;
+        }
+        return 50000e6;
+    }
+}