test: add APIConsumer unit tests with mock FunctionsRouter

test/FunctionConsumer.t.sol

@@ -0,0 +1,102 @@
+// SPDX-License-Identifier: MIT
+pragma solidity ^0.8.19;
+
+import "forge-std/Test.sol";
+import "../src/APIConsumer.sol";
+import {FunctionsRouter} from "@chainlink/functions/v1_0_0/FunctionsRouter.sol";
+
+contract MockFunctionsRouter is FunctionsRouter {
+    bytes32 public lastRequestId;
+    bytes public lastRequestCBOR;
+    uint64 public lastSubscriptionId;
+    uint32 public lastGasLimit;
+    bytes32 public lastDonId;
+
+    constructor() FunctionsRouter(address(0)) {}
+
+    function sendRequest(
+        uint64 subscriptionId,
+        bytes calldata requestCBOR,
+        uint32 gasLimit,
+        bytes32 donId
+    ) external returns (bytes32) {
+        lastRequestId = keccak256(abi.encodePacked(subscriptionId, requestCBOR, block.timestamp));
+        lastRequestCBOR = requestCBOR;
+        lastSubscriptionId = subscriptionId;
+        lastGasLimit = gasLimit;
+        lastDonId = donId;
+        return lastRequestId;
+    }
+
+    function simulateFulfillment(
+        bytes32 requestId,
+        address consumer,
+        bytes memory response,
+        bytes memory err
+    ) external {
+        APIConsumer(consumer).handleOracleFulfillment(requestId, response, err);
+    }
+}
+
+contract APIConsumerTest is Test {
+    MockFunctionsRouter public mockRouter;
+    APIConsumer public apiConsumer;
+
+    bytes32 public constant DON_ID = keccak256("test-don-id");
+    uint64 public constant SUBSCRIPTION_ID = 12345;
+
+    event RequestSent(bytes32 indexed requestId);
+    event ResponseReceived(bytes32 indexed requestId, bytes response, bytes err);
+
+    function setUp() public {
+        mockRouter = new MockFunctionsRouter();
+        apiConsumer = new APIConsumer(
+            address(mockRouter),
+            DON_ID,
+            SUBSCRIPTION_ID
+        );
+    }
+
+    function testInitialization() public {
+        assertEq(apiConsumer.donId(), DON_ID);
+        assertEq(apiConsumer.subscriptionId(), SUBSCRIPTION_ID);
+        assertEq(apiConsumer.gasLimit(), 300000);
+        assertEq(apiConsumer.owner(), address(this));
+    }
+
+    function testRequestAPIData() public {
+        string memory endpoint = "posts";
+        string memory id = "1";
+
+        vm.expectEmit(true, false, false, false);
+        emit RequestSent(bytes32(0))
+
+        bytes32 requestId = apiConsumer.requestAPIData(endpoint, id);
+
+        assertEq(mockRouter.lastSubscriptionId(), SUBSCRIPTION_ID);
+        assertEq(mockRouter.lastGasLimit(), 300000);
+        assertEq(mockRouter.lastDonId(), DON_ID);
+        assertTrue(mockRouter.lastRequestCBOR().length > 0);
+    }
+
+    function testFulfillRequest() public {
+
+        string memory endpoint = "posts";
+        string memory id = "1";
+        bytes32 requestId = apiConsumer.requestAPIData(endpoint, id);
+
+        bytes memory mockResponse = bytes('{"id":1,"title":"Test Post Title"}');
+        bytes memory emptyError = "";
+
+        vm.expectEmit(true, true, true, true);
+        emit ResponseReceived(requestId, mockResponse, emptyError);
+
+        mockRouter.simulateFulfillment(requestId, address(apiConsumer), mockResponse, emptyError);
+
+        assertEq(apiConsumer.lastResponse(), mockResponse);
+
+        string memory decodedResponse = apiConsumer.decodeResponse();
+        assertEq(decodedResponse, '{"id":1,"title":"Test Post Title"}');
+    }
+
+}