Testing Time

src/Time.sol

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+pragma solidity 0.8.20;
+
+contract Auction {
+    uint256 public startAt = block.timestamp + 1 days;
+    uint256 public endAt = block.timestamp + 2 days;
+
+    function bid() external {
+        require(block.timestamp >= startAt && block.timestamp < endAt, "cannot bid");
+    }
+
+    function end() external {
+        require(block.timestamp >= endAt, "cannot end");
+    }
+}
+

test/Time.t.sol

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+pragma solidity ^0.8.20;
+
+import "forge-std/Test.sol";
+import {Auction} from "../src/Time.sol";
+
+contract TimeTest is Test {
+    Auction public auction;
+    uint256 private startAt;
+
+    // vm.warp - set block.timestamp to future timestamp
+    // vm.roll - set block.number
+    // skip - increment current timestamp
+    // rewind - decrement current timestamp
+
+    function setUp() public {
+        auction = new Auction();
+        startAt = block.timestamp;
+    }
+
+    function testBidFailsBeforeStartTime() public {
+        vm.expectRevert(bytes("cannot bid"));
+        auction.bid();
+    }
+
+    function testBid() public {
+        vm.warp(startAt + 1 days);
+        auction.bid();
+    }
+    
+    function testBidFailsAfterEndTime() public {
+        vm.expectRevert(bytes("cannot bid"));
+        vm.warp(startAt + 2 days);
+        auction.bid();
+    }
+
+    function testAuctionEnds() public {
+        vm.warp(startAt + 3 days);
+        auction.end();
+    }
+
+    function testTimestamp() public {
+        uint t = block.timestamp;
+
+        // skip - increment current timestamp
+        skip(100);
+        assertEq(block.timestamp, t + 100);
+
+        // rewind - decrement current timestamp
+        rewind(10);
+        assertEq(block.timestamp, t + 100 - 10); 
+    }
+
+    function testBlockNumber() public {
+        // vm.roll - set block.number
+        uint b = block.number;
+        vm.roll(999);
+        assertEq(block.number, 999);
+    }
+    
+}