fix: state error undeclared class hash format

crates/blockifier/src/state.rs

@@ -1,4 +1,6 @@
 pub mod cached_state;
+#[cfg(test)]
+pub mod error_format_test;
 pub mod errors;
 pub mod global_cache;
 pub mod state_api;

crates/blockifier/src/state/error_format_test.rs

@@ -0,0 +1,14 @@
+use starknet_api::core::ClassHash;
+use starknet_types_core::felt::Felt;
+
+use crate::state::errors::StateError;
+
+#[test]
+fn test_error_undeclared_class_hash_format() {
+    let error = StateError::UndeclaredClassHash(ClassHash(Felt::TWO));
+    assert_eq!(
+        error.to_string(),
+        "Class with hash 0x0000000000000000000000000000000000000000000000000000000000000002 is \
+         not declared."
+    );
+}

crates/blockifier/src/state/errors.rs

@@ -21,7 +21,7 @@ pub enum StateError {
     ProgramError(#[from] ProgramError),
     #[error("Requested {0:?} is unavailable for deployment.")]
     UnavailableContractAddress(ContractAddress),
-    #[error("Class with hash {0} is not declared.")]
+    #[error("Class with hash {:#064x} is not declared.", **.0)]
     UndeclaredClassHash(ClassHash),
     #[error(transparent)]
     StarknetApiError(#[from] StarknetApiError),