diff --git a/Cargo.lock b/Cargo.lock
index 801d60deb3..6708a46367 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -10611,6 +10611,7 @@ dependencies = [
  "async-trait",
  "futures",
  "libp2p",
+ "mockall",
  "papyrus_config",
  "papyrus_network",
  "papyrus_network_types",
diff --git a/crates/starknet_mempool_p2p/Cargo.toml b/crates/starknet_mempool_p2p/Cargo.toml
index d934a4241f..e6f8e892f4 100644
--- a/crates/starknet_mempool_p2p/Cargo.toml
+++ b/crates/starknet_mempool_p2p/Cargo.toml
@@ -27,6 +27,7 @@ validator.workspace = true
 [dev-dependencies]
 futures.workspace = true
 libp2p.workspace = true
+mockall.workspace = true
 papyrus_network = { workspace = true, features = ["testing"] }
 papyrus_network_types = { workspace = true, features = ["testing"] }
 papyrus_protobuf.workspace = true
diff --git a/crates/starknet_mempool_p2p/src/runner/test.rs b/crates/starknet_mempool_p2p/src/runner/test.rs
index 5ad655c6fd..44f2c6f9e8 100644
--- a/crates/starknet_mempool_p2p/src/runner/test.rs
+++ b/crates/starknet_mempool_p2p/src/runner/test.rs
@@ -1,8 +1,6 @@
 use std::sync::Arc;
 use std::time::Duration;
 
-use async_trait::async_trait;
-use futures::channel::mpsc::Sender;
 use futures::future::{pending, ready, BoxFuture};
 use futures::stream::StreamExt;
 use futures::{FutureExt, SinkExt};
@@ -17,10 +15,10 @@ use papyrus_protobuf::mempool::RpcTransactionWrapper;
 use papyrus_test_utils::{get_rng, GetTestInstance};
 use starknet_api::rpc_transaction::RpcTransaction;
 use starknet_api::transaction::TransactionHash;
-use starknet_gateway_types::communication::{GatewayClient, GatewayClientResult};
+use starknet_gateway_types::communication::{GatewayClient, GatewayClientError, MockGatewayClient};
+use starknet_gateway_types::errors::{GatewayError, GatewaySpecError};
 use starknet_gateway_types::gateway_types::GatewayInput;
 use starknet_sequencer_infra::component_definitions::ComponentStarter;
-use tokio::time::sleep;
 
 use super::MempoolP2pRunner;
 
@@ -44,8 +42,7 @@ fn setup(
 #[test]
 fn run_returns_when_network_future_returns() {
     let network_future = ready(Ok(())).boxed();
-    let gateway_client =
-        Arc::new(MockGatewayClient { add_tx_sender: futures::channel::mpsc::channel(1).0 });
+    let gateway_client = Arc::new(MockGatewayClient::new());
     let (mut mempool_p2p_runner, _) = setup(network_future, gateway_client);
     mempool_p2p_runner.start().now_or_never().unwrap().unwrap();
 }
@@ -54,53 +51,110 @@ fn run_returns_when_network_future_returns() {
 fn run_returns_error_when_network_future_returns_error() {
     let network_future =
         ready(Err(NetworkError::DialError(libp2p::swarm::DialError::Aborted))).boxed();
-    let gateway_client =
-        Arc::new(MockGatewayClient { add_tx_sender: futures::channel::mpsc::channel(1).0 });
+    let gateway_client = Arc::new(MockGatewayClient::new());
     let (mut mempool_p2p_runner, _) = setup(network_future, gateway_client);
     mempool_p2p_runner.start().now_or_never().unwrap().unwrap_err();
 }
 
-// TODO(eitan): Make it an automock
-#[derive(Clone)]
-struct MockGatewayClient {
-    add_tx_sender: Sender<RpcTransaction>,
-}
+#[tokio::test]
+async fn incoming_p2p_tx_reaches_gateway_client() {
+    let network_future = pending().boxed();
+
+    // Create channels for sending an empty message to indicate that the tx reached the gateway
+    // client.
+    let (add_tx_indicator_sender, add_tx_indicator_receiver) = futures::channel::oneshot::channel();
+
+    let message_metadata = BroadcastedMessageMetadata::get_test_instance(&mut get_rng());
+    let expected_rpc_transaction =
+        RpcTransactionWrapper(RpcTransaction::get_test_instance(&mut get_rng()));
+    let gateway_input = GatewayInput {
+        rpc_tx: expected_rpc_transaction.0.clone(),
+        message_metadata: Some(message_metadata.clone()),
+    };
+
+    let mut mock_gateway_client = MockGatewayClient::new();
+    mock_gateway_client.expect_add_tx().with(mockall::predicate::eq(gateway_input)).return_once(
+        move |_| {
+            add_tx_indicator_sender.send(()).unwrap();
+            Ok(TransactionHash::default())
+        },
+    );
+    let (mut mempool_p2p_runner, mock_network) =
+        setup(network_future, Arc::new(mock_gateway_client));
+
+    let BroadcastNetworkMock {
+        broadcasted_messages_sender: mut mock_broadcasted_messages_sender,
+        ..
+    } = mock_network;
+
+    let res =
+        mock_broadcasted_messages_sender.send((expected_rpc_transaction.clone(), message_metadata));
 
-#[async_trait]
-impl GatewayClient for MockGatewayClient {
-    async fn add_tx(&self, gateway_input: GatewayInput) -> GatewayClientResult<TransactionHash> {
-        let _ = self.clone().add_tx_sender.send(gateway_input.rpc_tx).await;
-        Ok(TransactionHash::default())
+    res.await.expect("Failed to send message");
+
+    tokio::select! {
+        // if the runner fails, there was a network issue => panic.
+        // if the runner returns successfully, we panic because the runner should never terminate.
+        res = tokio::time::timeout(Duration::from_secs(5), mempool_p2p_runner.start()) => {
+            res.expect("Test timed out").expect("MempoolP2pRunner failed - network stopped unexpectedly");
+            panic!("MempoolP2pRunner terminated");
+        },
+        // if a message was received on this oneshot channel, the gateway client received the tx and the test succeeded.
+        res = add_tx_indicator_receiver => {res.unwrap()}
     }
 }
 
+// The p2p runner receives a tx from network, and the gateway declines it, triggering report_peer.
 #[tokio::test]
-async fn start_component_receive_tx_happy_flow() {
+async fn incoming_p2p_tx_fails_on_gateway_client() {
     let network_future = pending().boxed();
-    let (add_tx_sender, mut add_tx_receiver) = futures::channel::mpsc::channel(1);
-    let mock_gateway_client = Arc::new(MockGatewayClient { add_tx_sender });
-    let (mut mempool_p2p_runner, mock_network) = setup(network_future, mock_gateway_client);
+    // Create channels for sending an empty message to indicate that the tx reached the gateway
+    // client.
+    let (add_tx_indicator_sender, add_tx_indicator_receiver) = futures::channel::oneshot::channel();
+
+    let message_metadata = BroadcastedMessageMetadata::get_test_instance(&mut get_rng());
+    let message_metadata_clone = message_metadata.clone();
+    let expected_rpc_transaction =
+        RpcTransactionWrapper(RpcTransaction::get_test_instance(&mut get_rng()));
+
+    let mut mock_gateway_client = MockGatewayClient::new();
+    mock_gateway_client.expect_add_tx().return_once(move |_| {
+        add_tx_indicator_sender.send(()).unwrap();
+        Err(GatewayClientError::GatewayError(GatewayError::GatewaySpecError {
+            source: GatewaySpecError::DuplicateTx,
+            p2p_message_metadata: Some(message_metadata_clone),
+        }))
+    });
+
+    let (mut mempool_p2p_runner, mock_network) =
+        setup(network_future, Arc::new(mock_gateway_client));
+
     let BroadcastNetworkMock {
         broadcasted_messages_sender: mut mock_broadcasted_messages_sender,
+        reported_messages_receiver: mut mock_reported_messages_receiver,
         ..
     } = mock_network;
-    let message_metadata = BroadcastedMessageMetadata::get_test_instance(&mut get_rng());
-    let expected_rpc_transaction =
-        RpcTransactionWrapper(RpcTransaction::get_test_instance(&mut get_rng()));
 
-    // Sending the expected transaction to the mempool receiver
-    let res =
-        mock_broadcasted_messages_sender.send((expected_rpc_transaction.clone(), message_metadata));
+    let res = mock_broadcasted_messages_sender
+        .send((expected_rpc_transaction.clone(), message_metadata.clone()));
 
     res.await.expect("Failed to send message");
+
     tokio::select! {
-        _ = mempool_p2p_runner.start() => {panic!("Mempool receiver failed to start");}
-        actual_rpc_transaction = add_tx_receiver.next() => {
-            assert_eq!(actual_rpc_transaction, Some(expected_rpc_transaction.0));
-        }
-        _ = sleep(Duration::from_secs(5)) => {
-            panic!("Test timed out");
+        // if the runner fails, there was a network issue => panic.
+        // if the runner returns successfully, we panic because the runner should never terminate.
+        res = tokio::time::timeout(Duration::from_secs(5), mempool_p2p_runner.start()) => {
+            res.expect("Test timed out (MempoolP2pRunner took too long to start)").expect("MempoolP2pRunner failed - network stopped unexpectedly");
+            panic!("MempoolP2pRunner terminated");
+        },
+        // if a message was received on this oneshot channel, the gateway client received the tx.
+        res = add_tx_indicator_receiver => {
+            // if unwrap fails, the tx wasn't forwarded to the gateway client.
+            res.unwrap();
+            // After gateway client fails to add the tx, the p2p runner should have reported the peer.
+            let peer_reported = mock_reported_messages_receiver.next().await.expect("Failed to receive report");
+            // TODO: add this functionality to network manager test utils
+            assert_eq!(peer_reported, message_metadata.originator_id.private_get_peer_id())
         }
     }
 }
-// TODO(eitan): Add test for when the gateway client fails to add the transaction