add test for PaymentSplitter

test/PaymentSplitter.t.sol

@@ -0,0 +1,37 @@
+// SPDX-License-Identifier: AGPL-3.0-only
+pragma solidity ^0.8.13;
+
+import "../lib/forge-std/src/Test.sol";
+import "./resources/FakePaymentToken.sol";
+import "@openzeppelin/contracts/finance/PaymentSplitter.sol";
+
+contract paymentSplitterTest is Test {
+    FakePaymentToken token;
+
+    function setUp() public {
+        token = new FakePaymentToken(1000e18, 18);
+    }
+
+    function testFixedSplit() public {
+        address[] memory payees = new address[](2);
+        payees[0] = address(0x1);
+        payees[1] = address(0x2);
+        uint256[] memory shares = new uint256[](2);
+        shares[0] = 8; // 80%
+        shares[1] = 2; // 20%
+        PaymentSplitter splitter = new PaymentSplitter(payees, shares);
+
+        // send 100 tokens to the splitter
+        token.transfer(address(splitter), 100e18);
+
+        // pull share for address 1
+        assertEq(token.balanceOf(payees[0]), 0);
+        splitter.release(token, payees[0]);
+        assertEq(token.balanceOf(payees[0]), 80e18);
+
+        // pull share for address 2
+        assertEq(token.balanceOf(payees[1]), 0);
+        splitter.release(token, payees[1]);
+        assertEq(token.balanceOf(payees[1]), 20e18);
+    }
+}