diff --git a/test/forkMainnet/ConditionalSwap/Fill.t.sol b/test/forkMainnet/ConditionalSwap/Fill.t.sol
new file mode 100644
index 00000000..ecaf2777
--- /dev/null
+++ b/test/forkMainnet/ConditionalSwap/Fill.t.sol
@@ -0,0 +1,168 @@
+// SPDX-License-Identifier: MIT
+pragma solidity 0.8.17;
+
+import { IConditionalSwap } from "contracts/interfaces/IConditionalSwap.sol";
+import { ConditionalOrderSwapTest } from "test/forkMainnet/ConditionalSwap/Setup.t.sol";
+import { BalanceSnapshot, Snapshot } from "test/utils/BalanceSnapshot.sol";
+
+contract ConFillTest is ConditionalOrderSwapTest {
+    using BalanceSnapshot for Snapshot;
+
+    function setUp() public override {
+        super.setUp();
+    }
+
+    function testBestBuyOrder() external {
+        Snapshot memory takerTakerToken = BalanceSnapshot.take({ owner: taker, token: defaultOrder.takerToken });
+        Snapshot memory takerMakerToken = BalanceSnapshot.take({ owner: taker, token: defaultOrder.makerToken });
+        Snapshot memory makerTakerToken = BalanceSnapshot.take({ owner: maker, token: defaultOrder.takerToken });
+        Snapshot memory makerMakerToken = BalanceSnapshot.take({ owner: maker, token: defaultOrder.makerToken });
+        Snapshot memory recTakerToken = BalanceSnapshot.take({ owner: recipient, token: defaultOrder.takerToken });
+        Snapshot memory recMakerToken = BalanceSnapshot.take({ owner: recipient, token: defaultOrder.makerToken });
+
+        // craft the `flagAndPeriod` of the defaultOrder for BestBuy case
+        uint256 flags = 1 << 253;
+        defaultOrder.flagsAndPeriod = flags;
+
+        defaultTakerSig = signConOrder(takerPrivateKey, defaultOrder, address(conditionalSwap));
+
+        vm.startPrank(maker);
+        conditionalSwap.fillConOrder(defaultOrder, defaultTakerSig, defaultOrder.takerTokenAmount, defaultOrder.makerTokenAmount, defaultSettlementData);
+        vm.stopPrank();
+
+        takerTakerToken.assertChange(-int256(defaultOrder.takerTokenAmount));
+        takerMakerToken.assertChange(int256(0));
+        makerTakerToken.assertChange(int256(defaultOrder.takerTokenAmount));
+        makerMakerToken.assertChange(-int256(defaultOrder.makerTokenAmount));
+        recTakerToken.assertChange(int256(0));
+        recMakerToken.assertChange(int256(defaultOrder.makerTokenAmount));
+    }
+
+    function testRepayment() external {
+        Snapshot memory takerTakerToken = BalanceSnapshot.take({ owner: taker, token: defaultOrder.takerToken });
+        Snapshot memory takerMakerToken = BalanceSnapshot.take({ owner: taker, token: defaultOrder.makerToken });
+        Snapshot memory makerTakerToken = BalanceSnapshot.take({ owner: maker, token: defaultOrder.takerToken });
+        Snapshot memory makerMakerToken = BalanceSnapshot.take({ owner: maker, token: defaultOrder.makerToken });
+        Snapshot memory recTakerToken = BalanceSnapshot.take({ owner: recipient, token: defaultOrder.takerToken });
+        Snapshot memory recMakerToken = BalanceSnapshot.take({ owner: recipient, token: defaultOrder.makerToken });
+
+        // craft the `flagAndPeriod` of the defaultOrder for BestBuy case
+        uint256 flags = 7 << 253;
+        uint256 period = 12 hours;
+        uint256 numberOfCycles = (defaultExpiry - block.timestamp) / period;
+        defaultOrder.flagsAndPeriod = flags | period;
+
+        defaultTakerSig = signConOrder(takerPrivateKey, defaultOrder, address(conditionalSwap));
+        vm.startPrank(maker);
+        for (uint256 i; i < numberOfCycles; ++i) {
+            conditionalSwap.fillConOrder(defaultOrder, defaultTakerSig, defaultOrder.takerTokenAmount, defaultOrder.makerTokenAmount, defaultSettlementData);
+            vm.warp(block.timestamp + period);
+        }
+        vm.stopPrank();
+
+        takerTakerToken.assertChange(-int256(defaultOrder.takerTokenAmount) * int256(numberOfCycles));
+        takerMakerToken.assertChange(int256(0));
+        makerTakerToken.assertChange(int256(defaultOrder.takerTokenAmount) * int256(numberOfCycles));
+        makerMakerToken.assertChange(-int256(defaultOrder.makerTokenAmount) * int256(numberOfCycles));
+        recTakerToken.assertChange(int256(0));
+        recMakerToken.assertChange(int256(defaultOrder.makerTokenAmount) * int256(numberOfCycles));
+    }
+
+    function testDCAOrder() public {
+        // craft the `flagAndPeriod` of the defaultOrder for BestBuy case
+        uint256 flags = 7 << 253;
+        uint256 period = 1 days;
+
+        defaultOrder.flagsAndPeriod = flags | period;
+    }
+
+    function testCannotFillExpiredOrder() public {
+        vm.warp(defaultOrder.expiry + 1);
+
+        vm.expectRevert(IConditionalSwap.ExpiredOrder.selector);
+        vm.startPrank(maker);
+        conditionalSwap.fillConOrder(defaultOrder, defaultTakerSig, defaultOrder.takerTokenAmount, defaultOrder.makerTokenAmount, defaultSettlementData);
+        vm.stopPrank();
+    }
+
+    function testCannotFillOrderByInvalidOderMaker() public {
+        address invalidOrderMaker = makeAddr("invalidOrderMaker");
+
+        vm.expectRevert(IConditionalSwap.NotOrderMaker.selector);
+        vm.startPrank(invalidOrderMaker);
+        conditionalSwap.fillConOrder(defaultOrder, defaultTakerSig, defaultOrder.takerTokenAmount, defaultOrder.makerTokenAmount, defaultSettlementData);
+        vm.stopPrank();
+    }
+
+    function testCannotFillOrderWithZeroTakerTokenAmount() public {
+        vm.expectRevert(IConditionalSwap.ZeroTokenAmount.selector);
+        vm.startPrank(maker);
+        conditionalSwap.fillConOrder(defaultOrder, defaultTakerSig, 0, defaultOrder.makerTokenAmount, defaultSettlementData);
+        vm.stopPrank();
+    }
+
+    function testCannotFillOrderWithInvalidTotalTakerTokenAmount() public {
+        // craft the `flagAndPeriod` of the defaultOrder for BestBuy case
+        uint256 flags = 1 << 253;
+        defaultOrder.flagsAndPeriod = flags;
+
+        defaultTakerSig = signConOrder(takerPrivateKey, defaultOrder, address(conditionalSwap));
+
+        vm.startPrank(maker);
+        // the first fill with full takerTokenAmount
+        conditionalSwap.fillConOrder(defaultOrder, defaultTakerSig, defaultOrder.takerTokenAmount, defaultOrder.makerTokenAmount, defaultSettlementData);
+
+        vm.expectRevert(IConditionalSwap.InvalidTakingAmount.selector);
+        // The second fill with 1 takerTokenAmount would exceed the total cap this time.
+        conditionalSwap.fillConOrder(defaultOrder, defaultTakerSig, 1, defaultOrder.makerTokenAmount, defaultSettlementData);
+        vm.stopPrank();
+    }
+
+    function testCannotFillOrderWithInvalidSingleTakerTokenAmount() public {
+        // craft the `flagAndPeriod` of the defaultOrder for BestBuy case
+        uint256 flags = 7 << 253;
+        uint256 period = 12 hours;
+        defaultOrder.flagsAndPeriod = flags | period;
+
+        defaultTakerSig = signConOrder(takerPrivateKey, defaultOrder, address(conditionalSwap));
+
+        vm.expectRevert(IConditionalSwap.InvalidTakingAmount.selector);
+        vm.startPrank(maker);
+        conditionalSwap.fillConOrder(defaultOrder, defaultTakerSig, defaultOrder.takerTokenAmount + 1, defaultOrder.makerTokenAmount, defaultSettlementData);
+        vm.stopPrank();
+    }
+
+    function testCannotFillOrderWithInvalidZeroRecipient() public {
+        defaultOrder.recipient = payable(address(0));
+
+        vm.expectRevert(IConditionalSwap.InvalidRecipient.selector);
+        vm.startPrank(maker);
+        conditionalSwap.fillConOrder(defaultOrder, defaultTakerSig, defaultOrder.takerTokenAmount, defaultOrder.makerTokenAmount, defaultSettlementData);
+        vm.stopPrank();
+    }
+
+    function testCannotFillOrderWithIncorrectSignature() public {
+        uint256 randomPrivateKey = 1234;
+        bytes memory randomEOASig = signConOrder(randomPrivateKey, defaultOrder, address(conditionalSwap));
+
+        vm.expectRevert(IConditionalSwap.InvalidSignature.selector);
+        vm.startPrank(maker);
+        conditionalSwap.fillConOrder(defaultOrder, randomEOASig, defaultOrder.takerTokenAmount, defaultOrder.makerTokenAmount, defaultSettlementData);
+        vm.stopPrank();
+    }
+
+    function testCannotFillOrderWithinSamePeriod() public {
+        // craft the `flagAndPeriod` of the defaultOrder for BestBuy case
+        uint256 flags = 7 << 253;
+        uint256 period = 12 hours;
+        defaultOrder.flagsAndPeriod = flags | period;
+
+        defaultTakerSig = signConOrder(takerPrivateKey, defaultOrder, address(conditionalSwap));
+        vm.startPrank(maker);
+        conditionalSwap.fillConOrder(defaultOrder, defaultTakerSig, defaultOrder.takerTokenAmount, defaultOrder.makerTokenAmount, defaultSettlementData);
+        vm.warp(block.timestamp + 1);
+        vm.expectRevert(IConditionalSwap.InsufficientTimePassed.selector);
+        conditionalSwap.fillConOrder(defaultOrder, defaultTakerSig, defaultOrder.takerTokenAmount, defaultOrder.makerTokenAmount, defaultSettlementData);
+        vm.stopPrank();
+    }
+}
diff --git a/test/forkMainnet/ConditionalSwap/Setup.t.sol b/test/forkMainnet/ConditionalSwap/Setup.t.sol
new file mode 100644
index 00000000..ab94a083
--- /dev/null
+++ b/test/forkMainnet/ConditionalSwap/Setup.t.sol
@@ -0,0 +1,68 @@
+// SPDX-License-Identifier: MIT
+pragma solidity 0.8.17;
+
+import { Test } from "forge-std/Test.sol";
+import { IWETH } from "contracts/interfaces/IWETH.sol";
+import { IConditionalSwap } from "contracts/interfaces/IConditionalSwap.sol";
+import { ConditionalSwap } from "contracts/ConditionalSwap.sol";
+import { AllowanceTarget } from "contracts/AllowanceTarget.sol";
+import { ConOrder, getConOrderHash } from "contracts/libraries/ConditionalOrder.sol";
+import { Tokens } from "test/utils/Tokens.sol";
+import { BalanceUtil } from "test/utils/BalanceUtil.sol";
+import { SigHelper } from "test/utils/SigHelper.sol";
+import { computeContractAddress } from "test/utils/Addresses.sol";
+import { Permit2Helper } from "test/utils/Permit2Helper.sol";
+
+contract ConditionalOrderSwapTest is Test, Tokens, BalanceUtil, Permit2Helper, SigHelper {
+    // role
+    address public conditionalOrderOwner = makeAddr("conditionalOrderOwner");
+    address public allowanceTargetOwner = makeAddr("allowanceTargetOwner");
+    uint256 public takerPrivateKey = uint256(1);
+    uint256 public makerPrivateKey = uint256(2);
+    address public taker = vm.addr(takerPrivateKey);
+    address payable public maker = payable(vm.addr(makerPrivateKey));
+    address payable public recipient = payable(makeAddr("recipient"));
+
+    uint256 public defaultExpiry = block.timestamp + 1 days;
+    uint256 public defaultSalt = 1234;
+    bytes public defaultTakerPermit;
+    bytes public defaultTakerSig;
+    bytes public defaultSettlementData;
+
+    ConditionalSwap conditionalSwap;
+    AllowanceTarget allowanceTarget;
+    ConOrder defaultOrder;
+
+    function setUp() public virtual {
+        // deploy allowance target
+        address[] memory trusted = new address[](1);
+        // pre-compute ConditionalOrderSwap address since the whitelist of allowance target is immutable
+        // NOTE: this assumes LimitOrderSwap is deployed right next to Allowance Target
+        trusted[0] = computeContractAddress(address(this), uint8(vm.getNonce(address(this)) + 1));
+
+        allowanceTarget = new AllowanceTarget(allowanceTargetOwner, trusted);
+        conditionalSwap = new ConditionalSwap(conditionalOrderOwner, UNISWAP_PERMIT2_ADDRESS, address(allowanceTarget));
+
+        deal(maker, 100 ether);
+        deal(taker, 100 ether);
+        setTokenBalanceAndApprove(maker, address(conditionalSwap), tokens, 100000);
+        setTokenBalanceAndApprove(taker, address(conditionalSwap), tokens, 100000);
+
+        defaultTakerPermit = hex"01";
+        defaultSettlementData = hex"00";
+
+        defaultOrder = ConOrder({
+            taker: taker,
+            maker: maker,
+            recipient: recipient,
+            takerToken: USDT_ADDRESS,
+            takerTokenAmount: 10 * 1e6,
+            makerToken: DAI_ADDRESS,
+            makerTokenAmount: 10 ether,
+            takerTokenPermit: defaultTakerPermit,
+            flagsAndPeriod: 0,
+            expiry: defaultExpiry,
+            salt: defaultSalt
+        });
+    }
+}