add working fuzz test

Author: euler-mab

src/CurveLib.sol

@@ -113,12 +113,14 @@ library CurveLib {
     }
 
     function binarySearch(
-        uint256 y,
-        uint256 px,
-        uint256 py,
-        uint256 x0,
-        uint256 y0,
-        uint256 c,
+        IEulerSwap.Params memory p,
+        uint256 newReserve1,
+        // uint256 y,
+        // uint256 px,
+        // uint256 py,
+        // uint256 x0,
+        // uint256 y0,
+        // uint256 c,
         uint256 xMin,
         uint256 xMax
     ) internal pure returns (uint256) {
@@ -127,14 +129,14 @@ library CurveLib {
         }
         while (xMin < xMax) {
             uint256 xMid = (xMin + xMax) / 2;
-            uint256 fxMid = f(xMid, px, py, x0, y0, c);
-            if (y >= fxMid) {
+            uint256 fxMid = f(xMid, p.priceX, p.priceY, p.equilibriumReserve0, p.equilibriumReserve1, p.concentrationX);
+            if (newReserve1 >= fxMid) {
                 xMax = xMid;
             } else {
                 xMin = xMid + 1;
             }
         }
-        if (y < f(xMin, px, py, x0, y0, c)) {
+        if (newReserve1 < f(xMin, p.priceX, p.priceY, p.equilibriumReserve0, p.equilibriumReserve1, p.concentrationX)) {
             xMin += 1;
         }
         return xMin;

test/CurveLib.t.sol

@@ -4,6 +4,7 @@ pragma solidity ^0.8.24;
 import "forge-std/Test.sol";
 import "forge-std/console.sol";
 import {EulerSwapTestBase, EulerSwap, TestERC20} from "./EulerSwapTestBase.t.sol";
+import {IEulerSwap} from "../src/interfaces/IEulerSwap.sol";
 import {CurveLib} from "../src/CurveLib.sol";
 
 contract CurveLibTest is EulerSwapTestBase {
@@ -15,9 +16,8 @@ contract CurveLibTest is EulerSwapTestBase {
 
     function test_fuzzfInverse(uint256 x, uint256 px, uint256 py, uint256 x0, uint256 y0, uint256 cx, uint256 cy)
         public
-        pure
+        view
     {
-        
         // Params
         px = 1e18;
         py = bound(py, 1, 1e36);
@@ -32,6 +32,21 @@ contract CurveLibTest is EulerSwapTestBase {
         console.log("cx", cx);
         console.log("cy", cy);
 
+        IEulerSwap.Params memory p = IEulerSwap.Params({
+            vault0: address(0),
+            vault1: address(0),
+            eulerAccount: address(0),
+            equilibriumReserve0: uint112(x0),
+            equilibriumReserve1: uint112(y0),
+            priceX: px,
+            priceY: py,
+            concentrationX: cx,
+            concentrationY: cy,
+            fee: 0,
+            protocolFee: 0,
+            protocolFeeRecipient: address(0)
+        });
+
         // Note without -2 in the max bound, f() sometimes fails when x gets too close to centre.
         // Note small x values lead to large y-values, which causes problems for both f() and fInverse(), so we cap it here
         x = bound(x, 1e2 - 3, x0 - 3);
@@ -41,7 +56,7 @@ contract CurveLibTest is EulerSwapTestBase {
         uint256 xCalc = CurveLib.fInverse(y, px, py, x0, y0, cx);
         console.log("xCalc", xCalc);
         uint256 yCalc = CurveLib.f(xCalc, px, py, x0, y0, cx);
-        uint256 xBin = binarySearch(y, px, py, x0, y0, cx, 1, x0);
+        uint256 xBin = CurveLib.binarySearch(p, y, 1, x0);
         uint256 yBin = CurveLib.f(xBin, px, py, x0, y0, cx);
         console.log("x    ", x);
         console.log("xCalc", xCalc);
@@ -51,9 +66,8 @@ contract CurveLibTest is EulerSwapTestBase {
         console.log("yBin ", yBin);
 
         if (x < type(uint112).max && y < type(uint112).max) {
-            assert(CurveLib.verify(xCalc, y, x0, y0, px, py, cx, cy));
+            assert(CurveLib.verify(p, xCalc, y));
             assert(int256(xCalc) - int256(xBin) <= 3 || int256(yCalc) - int256(yBin) <= 3); // suspect this is 2 wei error in fInverse() + 1 wei error in f()
         }
     }
-
-}
+}