diff --git a/crates/primitives/src/chain.rs b/crates/primitives/src/chain.rs
index a88fb7dc44..40a974e903 100644
--- a/crates/primitives/src/chain.rs
+++ b/crates/primitives/src/chain.rs
@@ -137,3 +137,118 @@ impl Default for Chain {
         ethers_core::types::Chain::Mainnet.into()
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_id() {
+        let chain = Chain::Id(1234);
+        assert_eq!(chain.id(), 1234);
+    }
+
+    #[test]
+    fn test_named_id() {
+        let chain = Chain::Named(ethers_core::types::Chain::Goerli);
+        assert_eq!(chain.id(), 5);
+    }
+
+    #[test]
+    fn test_legacy_named_chain() {
+        let chain = Chain::Named(ethers_core::types::Chain::Optimism);
+        assert!(chain.is_legacy());
+    }
+
+    #[test]
+    fn test_not_legacy_named_chain() {
+        let chain = Chain::Named(ethers_core::types::Chain::Mainnet);
+        assert!(!chain.is_legacy());
+    }
+
+    #[test]
+    fn test_not_legacy_id_chain() {
+        let chain = Chain::Id(1234);
+        assert!(!chain.is_legacy());
+    }
+
+    #[test]
+    fn test_display_named_chain() {
+        let chain = Chain::Named(ethers_core::types::Chain::Mainnet);
+        assert_eq!(format!("{}", chain), "mainnet");
+    }
+
+    #[test]
+    fn test_display_id_chain() {
+        let chain = Chain::Id(1234);
+        assert_eq!(format!("{}", chain), "1234");
+    }
+
+    #[test]
+    fn test_from_u256() {
+        let n = U256::from(1234);
+        let chain = Chain::from(n);
+        let expected = Chain::Id(1234);
+
+        assert_eq!(chain, expected);
+    }
+
+    #[test]
+    fn test_into_u256() {
+        let chain = Chain::Named(ethers_core::types::Chain::Goerli);
+        let n: U256 = chain.into();
+        let expected = U256::from(5);
+
+        assert_eq!(n, expected);
+    }
+
+    #[test]
+    #[allow(non_snake_case)]
+    fn test_into_U64() {
+        let chain = Chain::Named(ethers_core::types::Chain::Goerli);
+        let n: U64 = chain.into();
+        let expected = U64::from(5);
+
+        assert_eq!(n, expected);
+    }
+
+    #[test]
+    fn test_from_str_named_chain() {
+        let result = Chain::from_str("mainnet");
+        let expected = Chain::Named(ethers_core::types::Chain::Mainnet);
+
+        assert!(result.is_ok());
+        assert_eq!(result.unwrap(), expected);
+    }
+
+    #[test]
+    fn test_from_str_named_chain_error() {
+        let result = Chain::from_str("chain");
+
+        assert!(result.is_err());
+    }
+
+    #[test]
+    fn test_from_str_id_chain() {
+        let result = Chain::from_str("1234");
+        let expected = Chain::Id(1234);
+
+        assert!(result.is_ok());
+        assert_eq!(result.unwrap(), expected);
+    }
+
+    #[test]
+    fn test_default() {
+        let default = Chain::default();
+        let expected = Chain::Named(ethers_core::types::Chain::Mainnet);
+
+        assert_eq!(default, expected);
+    }
+
+    #[test]
+    fn test_id_chain_encodable_length() {
+        let chain = Chain::Id(1234);
+
+        assert_eq!(chain.length(), 3);
+    }
+}