diff --git a/test/NftReward.t.sol b/test/NftReward.t.sol
index 262a3ae..3913a4a 100644
--- a/test/NftReward.t.sol
+++ b/test/NftReward.t.sol
@@ -655,4 +655,96 @@ contract NftRewardTest is Test {
         assertEq(nftReward.tokenIdCounter(), 1);
         assertEq(nftReward.tokenData(0, keccak256("GITHUB_ORGANIZATION_NAME")), "ubiquity");
     }
+
+    function testInvalidateNonce_ShouldInvalidateNonce() public {
+        // prepare arbitrary data keys
+        bytes32[] memory keys = new bytes32[](1);
+        keys[0] = keccak256("GITHUB_ORGANIZATION_NAME"); 
+        // prepare arbitrary data values
+        string[] memory values = new string[](1);
+        values[0] = "ubiquity";
+        // prepare mint request
+        NftReward.MintRequest memory mintRequest = NftReward.MintRequest({
+            beneficiary: user1,
+            deadline: block.timestamp + 1,
+            keys: keys,
+            nonce: 1,
+            values: values
+        });
+        // get mint request digest which should be signed
+        bytes32 digest = nftReward.getMintRequestDigest(mintRequest);
+        // minter signs mint request digest
+        (uint8 v, bytes32 r, bytes32 s) = vm.sign(minterPrivateKey, digest);
+        // get minter's signature
+        bytes memory signature = abi.encodePacked(r, s, v);
+
+        uint tokenId = 0;
+
+        // before
+        vm.expectRevert();
+        nftReward.ownerOf(tokenId);
+        assertEq(nftReward.nonceRedeemed(1), false);
+        assertEq(nftReward.tokenDataKeyExists(keccak256("GITHUB_ORGANIZATION_NAME")), false);
+
+        // owner invalidates
+        vm.prank(owner);
+        nftReward.invalidateNonce(1);
+
+        // user try to mint
+        vm.prank(user1);
+        vm.expectRevert("Already minted");
+        nftReward.safeMint(mintRequest, signature);
+
+        // after
+        assertEq(nftReward.nonceRedeemed(1), true);
+        assertEq(nftReward.tokenIdCounter(), 0);
+    }
+
+    function testRequireInvalidateNonce_ShouldRevert_IfNonceIsRedeemed() public {
+        // prepare arbitrary data keys
+        bytes32[] memory keys = new bytes32[](1);
+        keys[0] = keccak256("GITHUB_ORGANIZATION_NAME"); 
+        // prepare arbitrary data values
+        string[] memory values = new string[](1);
+        values[0] = "ubiquity";
+        // prepare mint request
+        NftReward.MintRequest memory mintRequest = NftReward.MintRequest({
+            beneficiary: user1,
+            deadline: block.timestamp + 1,
+            keys: keys,
+            nonce: 1,
+            values: values
+        });
+        // get mint request digest which should be signed
+        bytes32 digest = nftReward.getMintRequestDigest(mintRequest);
+        // minter signs mint request digest
+        (uint8 v, bytes32 r, bytes32 s) = vm.sign(minterPrivateKey, digest);
+        // get minter's signature
+        bytes memory signature = abi.encodePacked(r, s, v);
+
+        uint tokenId = 0;
+
+        // before
+        vm.expectRevert();
+        nftReward.ownerOf(tokenId);
+        assertEq(nftReward.nonceRedeemed(1), false);
+        assertEq(nftReward.tokenDataKeyExists(keccak256("GITHUB_ORGANIZATION_NAME")), false);
+
+        // user1 mints
+        vm.prank(user1);
+        nftReward.safeMint(mintRequest, signature);
+
+        // owner try to invalidate
+        vm.prank(owner);
+        vm.expectRevert("Already minted");
+        nftReward.invalidateNonce(1);
+
+        // after
+        assertEq(nftReward.nonceRedeemed(1), true);
+        assertEq(nftReward.tokenDataKeys(0), keccak256("GITHUB_ORGANIZATION_NAME"));
+        assertEq(nftReward.tokenDataKeyExists(keccak256("GITHUB_ORGANIZATION_NAME")), true);
+        assertEq(nftReward.ownerOf(tokenId), user1);
+        assertEq(nftReward.tokenIdCounter(), 1);
+        assertEq(nftReward.tokenData(0, keccak256("GITHUB_ORGANIZATION_NAME")), "ubiquity");
+    }
 }