fix: support parallel servers in tests

In order to add additional integration tests, the Web and RPC servers
must run on unique addresses, otherwise trying to create an additional
server will fail due to the socket already being in use.

This is achieved by selecting the port dynamically, through setting the
port as 0 (dynamic port), which `local_addr` then resolves into an
the actual port selected, that is, replacing `127.0.0.1:0` with
`127.0.0.1:<available_port_that_was_bound_by_TcpListener>`

crates/tests-integration/src/integration_test_utils.rs

@@ -13,6 +13,7 @@ use starknet_gateway::errors::GatewayError;
 use starknet_gateway::gateway::Gateway;
 use starknet_mempool_types::communication::SharedMempoolClient;
 use test_utils::starknet_api_test_utils::external_tx_to_json;
+use tokio::net::TcpListener;
 
 use crate::state_reader::rpc_test_state_reader_factory;
 
@@ -27,7 +28,7 @@ pub async fn create_gateway(
         ..Default::default()
     };
 
-    let socket: SocketAddr = "127.0.0.1:3000".parse().unwrap();
+    let socket = get_available_socket().await;
     let network_config = GatewayNetworkConfig { ip: socket.ip(), port: socket.port() };
     let stateful_tx_validator_config = StatefulTransactionValidatorConfig::create_for_testing();
 
@@ -80,3 +81,18 @@ impl GatewayClient {
             .unwrap()
     }
 }
+
+/// Returns a unique IP address and port for testing purposes.
+///
+/// Tests run in parallel, so servers (like RPC or web) running on separate tests must have
+/// different ports, otherwise the server will fail with "address already in use".
+pub async fn get_available_socket() -> SocketAddr {
+    // Dinamically select port.
+    // First, set the port to 0 (dynamic port).
+    TcpListener::bind("127.0.0.1:0")
+        .await
+        .expect("Failed to bind to address")
+        // Then, resolve to the actual selected port.
+        .local_addr()
+        .expect("Failed to get local address")
+}

crates/tests-integration/src/state_reader.rs

@@ -36,6 +36,8 @@ use tempfile::tempdir;
 use test_utils::starknet_api_test_utils::{deploy_account_tx, deployed_account_contract_address};
 use tokio::sync::RwLock;
 
+use crate::integration_test_utils::get_available_socket;
+
 type ContractClassesMap =
     (Vec<(ClassHash, DeprecatedContractClass)>, Vec<(ClassHash, CasmContractClass)>);
 
@@ -306,7 +308,10 @@ fn get_test_pending_classes() -> Arc<RwLock<PendingClasses>> {
 }
 
 async fn run_papyrus_rpc_server(storage_reader: StorageReader) -> SocketAddr {
-    let rpc_config = RpcConfig::default();
+    let rpc_config = RpcConfig {
+        server_address: get_available_socket().await.to_string(),
+        ..Default::default()
+    };
     let (addr, handle) = run_server(
         &rpc_config,
         get_test_highest_block(),