diff --git a/.github/workflows/tee-worker-ci.yml b/.github/workflows/tee-worker-ci.yml
index 581c43bf73..81ceb761f5 100644
--- a/.github/workflows/tee-worker-ci.yml
+++ b/.github/workflows/tee-worker-ci.yml
@@ -58,6 +58,7 @@ jobs:
   build-parachain-docker:
     runs-on: ubuntu-latest
     needs: check-file-change
+    if: needs.check-file-change.outputs.src == 'true'
     steps:
       - uses: actions/checkout@v3
 
@@ -78,6 +79,7 @@ jobs:
   build-test:
     runs-on: ubuntu-20.04
     needs: check-file-change
+    if: needs.check-file-change.outputs.src == 'true'
     strategy:
       fail-fast: false
       matrix:
@@ -140,6 +142,7 @@ jobs:
   clippy:
     runs-on: ubuntu-latest
     needs: check-file-change
+    if: needs.check-file-change.outputs.src == 'true'
     container: "integritee/integritee-dev:0.1.9"
     steps:
       - uses: actions/checkout@v3
@@ -175,6 +178,7 @@ jobs:
   fmt:
     runs-on: ubuntu-latest
     needs: check-file-change
+    if: needs.check-file-change.outputs.src == 'true'
     steps:
       - uses: actions/checkout@v3
       - name: init rust
diff --git a/pallets/identity-management-mock/src/mock.rs b/pallets/identity-management-mock/src/mock.rs
index 20cd46aa83..5a1e59bc89 100644
--- a/pallets/identity-management-mock/src/mock.rs
+++ b/pallets/identity-management-mock/src/mock.rs
@@ -16,7 +16,7 @@
 
 #![cfg(test)]
 
-use crate::{
+pub use crate::{
 	self as pallet_identity_management_mock,
 	key::{aes_encrypt_default, tee_encrypt},
 	ChallengeCode,
@@ -32,7 +32,7 @@ use frame_support::{
 	traits::{ConstU128, ConstU16, ConstU32, ConstU64, Everything},
 };
 use frame_system as system;
-use mock_tee_primitives::{
+pub use mock_tee_primitives::{
 	EthereumSignature, EvmNetwork, Identity, IdentityHandle, IdentityMultiSignature,
 	IdentityWebType, SubstrateNetwork, TwitterValidationData, UserShieldingKeyType, ValidationData,
 	Web2Network, Web2ValidationData, Web3CommonValidationData, Web3Network, Web3ValidationData,
@@ -142,11 +142,11 @@ pub fn new_test_ext() -> sp_io::TestExternalities {
 	ext
 }
 
-pub fn create_mock_twitter_identity() -> Identity {
+pub fn create_mock_twitter_identity(twitter_handle: &[u8]) -> Identity {
 	Identity {
 		web_type: IdentityWebType::Web2(Web2Network::Twitter),
 		handle: IdentityHandle::String(
-			b"aliceTwitterHandle".to_vec().try_into().expect("convert to BoundedVec failed"),
+			twitter_handle.to_vec().try_into().expect("convert to BoundedVec failed"),
 		),
 	}
 }
diff --git a/pallets/identity-management-mock/src/tests.rs b/pallets/identity-management-mock/src/tests.rs
index 4a88c52154..0f71ba40dd 100644
--- a/pallets/identity-management-mock/src/tests.rs
+++ b/pallets/identity-management-mock/src/tests.rs
@@ -16,8 +16,9 @@
 
 use crate::{mock::*, Error};
 
+use codec::Encode;
 use frame_support::assert_noop;
-use sp_core::{Pair, H256};
+use sp_core::{blake2_256, Pair, H256};
 
 #[test]
 fn unpriveledged_origin_call_fails() {
@@ -50,7 +51,7 @@ fn set_user_shielding_key_works() {
 fn link_twitter_identity_works() {
 	new_test_ext().execute_with(|| {
 		System::set_block_number(5);
-		setup_link_identity(2, create_mock_twitter_identity(), 5);
+		setup_link_identity(2, create_mock_twitter_identity(b"alice"), 5);
 	});
 }
 
@@ -78,7 +79,7 @@ fn link_eth_identity_works() {
 fn verify_twitter_identity_works() {
 	new_test_ext().execute_with(|| {
 		System::set_block_number(3);
-		setup_verify_twitter_identity(2, create_mock_twitter_identity(), 3);
+		setup_verify_twitter_identity(2, create_mock_twitter_identity(b"alice"), 3);
 	});
 }
 
@@ -99,3 +100,53 @@ fn verify_eth_identity_works() {
 		setup_verify_eth_identity(2, p, 4);
 	});
 }
+
+#[test]
+fn double_link_twitter_identity_works() {
+	new_test_ext().execute_with(|| {
+		// link and verify the first twitter handle
+		System::set_block_number(3);
+		setup_verify_twitter_identity(2, create_mock_twitter_identity(b"alice"), 3);
+		// link second twitter handle works
+		System::set_block_number(4);
+		setup_link_identity(2, create_mock_twitter_identity(b"bob"), 4);
+	});
+}
+
+#[test]
+fn wrong_polkadot_verification_message_fails() {
+	new_test_ext().execute_with(|| {
+		System::set_block_number(3);
+		let p = sp_core::sr25519::Pair::from_string("//Alice", None).unwrap();
+		let identity = create_mock_polkadot_identity(p.public().0);
+		let who = 2;
+		setup_link_identity(who, identity.clone(), 3);
+
+		System::set_block_number(4);
+		let encrypted_identity = tee_encrypt(identity.encode().as_slice());
+
+		// intentionally construct a wrong verification message
+		let wrong_msg = blake2_256(&[0u8; 16]).to_vec();
+		let sig = p.sign(&wrong_msg);
+		let common_validation_data = Web3CommonValidationData {
+			message: wrong_msg.try_into().unwrap(),
+			signature: IdentityMultiSignature::Sr25519(sig),
+		};
+
+		let validation_data = match &identity.web_type {
+			IdentityWebType::Web3(Web3Network::Substrate(SubstrateNetwork::Polkadot)) =>
+				ValidationData::Web3(Web3ValidationData::Substrate(common_validation_data)),
+			_ => panic!("unxpected web_type"),
+		};
+
+		assert_noop!(
+			IdentityManagementMock::verify_identity(
+				Origin::signed(who),
+				H256::random(),
+				encrypted_identity,
+				tee_encrypt(validation_data.encode().as_slice()),
+			),
+			Error::<Test>::UnexpectedMessage
+		);
+	});
+}