added integration tests

test/CarbonIntegrationTest.sol

@@ -0,0 +1,103 @@
+// SPDX-License-Identifier: MIT
+pragma solidity ^0.8.19;
+
+import "forge-std/Test.sol";
+import "../src/Controller.sol";
+import "../test/MockUSDC.sol";
+
+contract CarbonIntegrationTest is Test {
+   Controller public controller;
+   MockUSDC public usdc;
+   address public owner;
+   address public priceOracle;
+   address public tesla1;
+   address public tesla2;
+   address public buyer;
+
+   function setUp() public {
+       // Create addresses
+       owner = makeAddr("owner");
+       priceOracle = makeAddr("priceOracle");
+       tesla1 = makeAddr("tesla1");
+       tesla2 = makeAddr("tesla2");
+       buyer = makeAddr("buyer");
+
+       vm.startPrank(owner);
+
+       // Deploy system
+       usdc = new MockUSDC();
+       controller = new Controller(address(usdc), priceOracle);
+
+       // Fund buyer with USDC
+       usdc.transfer(buyer, 10000 * 10**6); // 10k USDC
+
+       vm.stopPrank();
+   }
+
+   function test_CompleteFlow() public {
+       // Step 2: Process odometer readings - Add Queue verification
+       vm.startPrank(owner);
+
+       // Tesla1 drives 350 miles (3 credits)
+       controller.registerVehicle(tesla1, "TESLA2023_1");
+       controller.processOdometerReading(tesla1, 350);
+       assertEq(controller.carbonQueue()._getAvailableCredits(), 3, "Queue should have 3 credits after Tesla1");
+
+       // Tesla2 drives 250 miles (2 credits)
+       controller.registerVehicle(tesla2, "TESLA2023_2");
+       controller.processOdometerReading(tesla2, 250);
+       assertEq(controller.carbonQueue()._getAvailableCredits(), 5, "Queue should have 5 total credits");
+
+       // Verify the first credit in queue belongs to Tesla1
+       (address queueFirstHolder,, bool isValid) = controller.carbonQueue()._getCreditDetails(0);
+       assertEq(queueFirstHolder, tesla1, "First credit should belong to Tesla1");
+       assertTrue(isValid, "First credit should be valid");
+
+       // Verify a later credit belongs to Tesla2
+       (address queueLaterHolder,,) = controller.carbonQueue()._getCreditDetails(3);
+       assertEq(queueLaterHolder, tesla2, "Fourth credit should belong to Tesla2");
+
+       vm.stopPrank();
+
+       // Step 3: Buyer purchases 4 credits - Add Queue verification
+       vm.startPrank(buyer);
+       usdc.approve(address(controller), 1000 * 10**6);
+       controller.burnCredit(4);
+
+       // Verify Queue state after burning
+       assertEq(controller.carbonQueue()._getAvailableCredits(), 1, "Queue should have 1 credit left");
+
+       // Verify first 4 credits are now invalid
+       (,, bool isValidAfterBurn) = controller.carbonQueue()._getCreditDetails(0);
+       assertFalse(isValidAfterBurn, "First credit should be invalid after burn");
+
+       // Verify the remaining credit belongs to Tesla2 and is still valid
+       (address remainingHolder,, bool remainingValid) = controller.carbonQueue()._getCreditDetails(4);
+       assertEq(remainingHolder, tesla2, "Remaining credit should belong to Tesla2");
+       assertTrue(remainingValid, "Remaining credit should be valid");
+
+       vm.stopPrank();
+
+       // Step 4: Both Tesla owners withdraw their rewards
+       uint256 tesla1InitialBalance = usdc.balanceOf(tesla1);
+       uint256 tesla2InitialBalance = usdc.balanceOf(tesla2);
+
+       vm.prank(tesla1);
+       controller.withdrawRewards();
+
+       vm.prank(tesla2);
+       controller.withdrawRewards();
+
+       // Verify final states
+       assertEq(
+           usdc.balanceOf(tesla1), 
+           tesla1InitialBalance + (3 * 100 * 10**6), 
+           "Tesla1 should have received 300 USDC"
+       );
+       assertEq(
+           usdc.balanceOf(tesla2), 
+           tesla2InitialBalance + (1 * 100 * 10**6), 
+           "Tesla2 should have received 100 USDC"
+       );
+   }
+}