Forge - test against coingecko prices

contracts/test/oracles/default/ChainlinkOracleTest.t.sol

@@ -5,8 +5,9 @@ import { ChainlinkPriceOracleV2 } from "../../../oracles/default/ChainlinkPriceO
 import { ICToken } from "../../../external/compound/ICToken.sol";
 
 import { BaseTest } from "../../config/BaseTest.t.sol";
+import { CoingeckoAPICaller } from "./CoingeckoAPICaller.sol";
 
-contract ChainlinkOraclesTest is BaseTest {
+contract ChainlinkOraclesTest is BaseTest, CoingeckoAPICaller {
   ChainlinkPriceOracleV2 oracle;
 
   address usdcPolygon = 0x2791Bca1f2de4661ED88A30C99A7a9449Aa84174;
@@ -75,4 +76,11 @@ contract ChainlinkOraclesTest is BaseTest {
 
     assertApproxEqAbs(usdtPrice, usdcPrice, 1e16, "usd prices differ too much");
   }
+
+  function testPriceAgainstCoingecko() public debuggingOnly {
+    string memory base = "usd";
+    string memory asset = "ethereum-classic";
+    uint256 price = getCoinGeckoPrice(asset, base); // scaled to 1e18
+    emit log_named_uint("ethereum-classic price in usd", price);
+  }
 }

contracts/test/oracles/default/CoingeckoAPICaller.sol

@@ -0,0 +1,49 @@
+// SPDX-License-Identifier: UNLICENSED
+pragma solidity >=0.8.0;
+
+import "forge-std/Vm.sol";
+import "forge-std/Test.sol";
+
+contract CoingeckoAPICaller is Test {
+  string internal constant COINGECKO_BASE_URL = "https://api.coingecko.com/api/v3/simple/price?vs_currencies=";
+  string internal constant PRECISION_QUERY_URL = "&precision=18&ids=";
+
+  function getCoinGeckoPrice(string memory asset, string memory base) internal returns (uint256) {
+    string memory url = concat4(COINGECKO_BASE_URL, base, PRECISION_QUERY_URL, asset);
+    string[] memory command = new string[](2);
+    command[0] = "curl";
+    command[1] = url;
+
+    string memory response = string(vm.ffi(command));
+    emit log_named_string("response", response);
+    string memory jqFilter = concat4(".", asset, ".", base);
+    string memory floatPointPrice = string(vm.parseJsonString(response, jqFilter));
+    return floatPointToUint(floatPointPrice);
+  }
+
+  function concat4(
+    string memory str0,
+    string memory str1,
+    string memory str2,
+    string memory str3
+  ) internal returns (string memory) {
+    return string(bytes.concat(bytes.concat(bytes(str0), bytes(str1)), bytes.concat(bytes(str2), bytes(str3))));
+  }
+
+  function floatPointToUint(string memory str) internal returns (uint256) {
+    bytes memory asBytes = bytes(str);
+    uint256 k;
+
+    for (uint256 i = 0; i < asBytes.length; i++) {
+      if (asBytes[i] != ".") k++;
+    }
+
+    bytes memory noPointBytes = new bytes(k);
+    k = 0;
+    for (uint256 i = 0; i < asBytes.length; i++) {
+      if (asBytes[i] != ".") noPointBytes[k++] = asBytes[i];
+    }
+
+    return vm.parseUint(string(noPointBytes));
+  }
+}