chore: added unit tests for PPMMath

Author: Maikol

packages/horizon/test/libraries/PPMMath.t.sol

@@ -0,0 +1,46 @@
+// SPDX-License-Identifier: UNLICENSED
+pragma solidity 0.8.27;
+
+import "forge-std/console.sol";
+import { Test } from "forge-std/Test.sol";
+import { PPMMath } from "../../contracts/libraries/PPMMath.sol";
+
+contract PPMMathTest is Test {
+    uint32 private constant MAX_PPM = 1000000;
+
+    function test_mulPPM(uint256 a, uint256 b) public pure {
+        a = bound(a, 0, MAX_PPM);
+        b = bound(b, 0, type(uint256).max / MAX_PPM);
+        
+        uint256 result = PPMMath.mulPPM(a, b);
+        assertEq(result, (a * b) / MAX_PPM);
+    }
+
+    function test_mulPPMRoundUp(uint256 a, uint256 b) public pure {
+        a = bound(a, 0, type(uint256).max / MAX_PPM);
+        b = bound(b, 0, MAX_PPM);
+        
+        uint256 result = PPMMath.mulPPMRoundUp(a, b);
+        assertEq(result, a - PPMMath.mulPPM(a, MAX_PPM - b));
+    }
+
+    function test_isValidPPM(uint256 value) public pure {
+        bool result = PPMMath.isValidPPM(value);
+        assert(result == (value <= MAX_PPM));
+    }
+
+    function test_mullPPM_RevertWhen_InvalidPPM(uint256 a, uint256 b) public {
+        a = bound(a, MAX_PPM + 1, type(uint256).max);
+        b = bound(b, MAX_PPM + 1, type(uint256).max);
+        bytes memory expectedError = abi.encodeWithSelector(PPMMath.PPMMathInvalidMulPPM.selector, a, b);
+        vm.expectRevert(expectedError);
+        PPMMath.mulPPM(a, b);
+    }
+
+    function test_mullPPMRoundUp_RevertWhen_InvalidPPM(uint256 a, uint256 b) public {
+        b = bound(b, MAX_PPM + 1, type(uint256).max);
+        bytes memory expectedError = abi.encodeWithSelector(PPMMath.PPMMathInvalidPPM.selector, b);
+        vm.expectRevert(expectedError);
+        PPMMath.mulPPMRoundUp(a, b);
+    }
+}