diff --git a/world-chain-builder/Cargo.lock b/world-chain-builder/Cargo.lock
index 6638b20b..87285e82 100644
--- a/world-chain-builder/Cargo.lock
+++ b/world-chain-builder/Cargo.lock
@@ -10064,6 +10064,15 @@ dependencies = [
  "syn 1.0.109",
 ]
 
+[[package]]
+name = "scc"
+version = "2.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "836f1e0f4963ef5288b539b643b35e043e76a32d0f4e47e67febf69576527f50"
+dependencies = [
+ "sdd",
+]
+
 [[package]]
 name = "schannel"
 version = "0.1.26"
@@ -10121,6 +10130,12 @@ version = "1.0.7"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "a3cf7c11c38cb994f3d40e8a8cde3bbd1f72a435e4c49e85d6553d8312306152"
 
+[[package]]
+name = "sdd"
+version = "3.0.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "60a7b59a5d9b0099720b417b6325d91a52cbf5b3dcb5041d864be53eefa58abc"
+
 [[package]]
 name = "seahash"
 version = "4.1.0"
@@ -10430,6 +10445,31 @@ dependencies = [
  "unsafe-libyaml",
 ]
 
+[[package]]
+name = "serial_test"
+version = "3.1.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4b4b487fe2acf240a021cf57c6b2b4903b1e78ca0ecd862a71b71d2a51fed77d"
+dependencies = [
+ "futures",
+ "log",
+ "once_cell",
+ "parking_lot 0.12.3",
+ "scc",
+ "serial_test_derive",
+]
+
+[[package]]
+name = "serial_test_derive"
+version = "3.1.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "82fe9db325bcef1fbcde82e078a5cc4efdf787e96b3b9cf45b50b529f2083d67"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn 2.0.79",
+]
+
 [[package]]
 name = "sha1"
 version = "0.10.6"
@@ -12997,6 +13037,7 @@ dependencies = [
  "semaphore",
  "serde",
  "serde_json",
+ "serial_test",
  "strum",
  "strum_macros",
  "tempfile",
diff --git a/world-chain-builder/Cargo.toml b/world-chain-builder/Cargo.toml
index 54d044fa..2c63693e 100644
--- a/world-chain-builder/Cargo.toml
+++ b/world-chain-builder/Cargo.toml
@@ -91,6 +91,7 @@ bytes = "1.7.2"
 hex = "0.4.3"
 
 [dev-dependencies]
+serial_test = "3"
 tempfile = "3"
 test-case = "3"
 ethers-core = { git = "https://github.com/gakonst/ethers-rs", default-features = false }
diff --git a/world-chain-builder/src/e2e_tests/mod.rs b/world-chain-builder/src/e2e_tests/mod.rs
index 2749c03c..ec076af2 100644
--- a/world-chain-builder/src/e2e_tests/mod.rs
+++ b/world-chain-builder/src/e2e_tests/mod.rs
@@ -51,6 +51,7 @@ use semaphore::{
     protocol::{generate_nullifier_hash, generate_proof},
     Field,
 };
+use serial_test::serial;
 use std::{
     collections::{BTreeMap, HashMap},
     sync::Arc,
@@ -227,6 +228,7 @@ impl WorldChainBuilderTestContext {
 }
 
 #[tokio::test]
+#[serial]
 async fn test_can_build_pbh_payload() -> eyre::Result<()> {
     tokio::time::sleep(Duration::from_secs(1)).await;
     let mut ctx = WorldChainBuilderTestContext::setup().await?;
@@ -255,6 +257,7 @@ async fn test_can_build_pbh_payload() -> eyre::Result<()> {
 }
 
 #[tokio::test]
+#[serial]
 async fn test_transaction_pool_ordering() -> eyre::Result<()> {
     tokio::time::sleep(Duration::from_secs(1)).await;
     let mut ctx = WorldChainBuilderTestContext::setup().await?;
@@ -298,6 +301,7 @@ async fn test_transaction_pool_ordering() -> eyre::Result<()> {
 }
 
 #[tokio::test]
+#[serial]
 async fn test_invalidate_dup_tx_and_nullifier() -> eyre::Result<()> {
     tokio::time::sleep(Duration::from_secs(1)).await;
     let ctx = WorldChainBuilderTestContext::setup().await?;
@@ -310,6 +314,7 @@ async fn test_invalidate_dup_tx_and_nullifier() -> eyre::Result<()> {
 }
 
 #[tokio::test]
+#[serial]
 async fn test_dup_pbh_nonce() -> eyre::Result<()> {
     tokio::time::sleep(Duration::from_secs(1)).await;
     let mut ctx = WorldChainBuilderTestContext::setup().await?;
diff --git a/world-chain-builder/src/pool/validator.rs b/world-chain-builder/src/pool/validator.rs
index 483e3e30..2d34dd09 100644
--- a/world-chain-builder/src/pool/validator.rs
+++ b/world-chain-builder/src/pool/validator.rs
@@ -561,24 +561,6 @@ pub mod tests {
         assert!(res.is_err());
     }
 
-    #[test]
-    fn validate_external_nullifier_hash_mismatch() {
-        let external_nullifier = "v1-012025-1";
-
-        let validator = world_chain_validator();
-        let date = chrono::Utc.with_ymd_and_hms(2025, 1, 1, 0, 0, 0).unwrap();
-
-        let payload = PbhPayload {
-            external_nullifier: external_nullifier.to_string(),
-            nullifier_hash: Field::ZERO,
-            root: Field::ZERO,
-            proof: Default::default(),
-        };
-
-        let res = validator.validate_external_nullifier(date, &payload);
-        assert!(res.is_err());
-    }
-
     #[test_case("v1-012025-0")]
     #[test_case("v1-012025-1")]
     #[test_case("v1-012025-29")]