diff --git a/ethers-etherscan/Cargo.toml b/ethers-etherscan/Cargo.toml
index ed9dd2a9..dae64a8f 100644
--- a/ethers-etherscan/Cargo.toml
+++ b/ethers-etherscan/Cargo.toml
@@ -22,7 +22,7 @@ serde-aux = { version = "3.0.1", default-features = false }
 thiserror = "1.0.29"
 
 [dev-dependencies]
-tokio = { version = "1.5", features = ["macros", "rt-multi-thread"] }
+tokio = { version = "1.5", features = ["macros", "rt-multi-thread", "time"] }
 serial_test = "0.5.1"
 
 [package.metadata.docs.rs]
diff --git a/ethers-etherscan/src/contract.rs b/ethers-etherscan/src/contract.rs
index d9e18bd3..1e3c7a4b 100644
--- a/ethers-etherscan/src/contract.rs
+++ b/ethers-etherscan/src/contract.rs
@@ -1,8 +1,11 @@
-use crate::{Client, Response, Result};
-use ethers_core::abi::{Abi, Address};
-use serde::{Deserialize, Serialize};
 use std::collections::HashMap;
 
+use serde::{Deserialize, Serialize};
+
+use ethers_core::abi::{Abi, Address};
+
+use crate::{Client, Response, Result};
+
 /// Arguments for verifying contracts
 #[derive(Debug, Clone, Serialize)]
 pub struct VerifyContract {
@@ -251,55 +254,66 @@ impl Client {
 
 #[cfg(test)]
 mod tests {
-    use crate::{contract::VerifyContract, Client};
-    use ethers_core::types::Chain;
+    use std::time::Duration;
 
     use serial_test::serial;
 
+    use ethers_core::types::Chain;
+
+    use crate::{contract::VerifyContract, tests::run_at_least_duration, Client};
+
     #[tokio::test]
     #[serial]
     #[ignore]
     async fn can_fetch_contract_abi() {
-        let client = Client::new_from_env(Chain::Mainnet).unwrap();
+        run_at_least_duration(Duration::from_millis(200), async {
+            let client = Client::new_from_env(Chain::Mainnet).unwrap();
 
-        let _abi = client
-            .contract_abi("0xBB9bc244D798123fDe783fCc1C72d3Bb8C189413".parse().unwrap())
-            .await
-            .unwrap();
+            let _abi = client
+                .contract_abi("0xBB9bc244D798123fDe783fCc1C72d3Bb8C189413".parse().unwrap())
+                .await
+                .unwrap();
+        })
+        .await;
     }
 
     #[tokio::test]
     #[serial]
     #[ignore]
     async fn can_fetch_contract_source_code() {
-        let client = Client::new_from_env(Chain::Mainnet).unwrap();
+        run_at_least_duration(Duration::from_millis(200), async {
+            let client = Client::new_from_env(Chain::Mainnet).unwrap();
 
-        let _meta = client
-            .contract_source_code("0xBB9bc244D798123fDe783fCc1C72d3Bb8C189413".parse().unwrap())
-            .await
-            .unwrap();
+            let _meta = client
+                .contract_source_code("0xBB9bc244D798123fDe783fCc1C72d3Bb8C189413".parse().unwrap())
+                .await
+                .unwrap();
+        })
+        .await
     }
 
     #[tokio::test]
     #[serial]
     #[ignore]
     async fn can_verify_contract() {
-        // TODO this needs further investigation
+        run_at_least_duration(Duration::from_millis(200), async {
+            // TODO this needs further investigation
 
-        // https://etherscan.io/address/0x9e744c9115b74834c0f33f4097f40c02a9ac5c33#code
-        let contract = include_str!("../resources/UniswapExchange.sol");
-        let address = "0x9e744c9115b74834c0f33f4097f40c02a9ac5c33".parse().unwrap();
-        let compiler_version = "v0.5.17+commit.d19bba13";
-        let constructor_args = "0x000000000000000000000000000000000000000000000000000000000000006000000000000000000000000000000000000000000000000000000000000000a00000000000000000000000000000000000000000000000000000000005f5e1000000000000000000000000000000000000000000000000000000000000000007596179537761700000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000035941590000000000000000000000000000000000000000000000000000000000";
+            // https://etherscan.io/address/0x9e744c9115b74834c0f33f4097f40c02a9ac5c33#code
+            let contract = include_str!("../resources/UniswapExchange.sol");
+            let address = "0x9e744c9115b74834c0f33f4097f40c02a9ac5c33".parse().unwrap();
+            let compiler_version = "v0.5.17+commit.d19bba13";
+            let constructor_args = "0x000000000000000000000000000000000000000000000000000000000000006000000000000000000000000000000000000000000000000000000000000000a00000000000000000000000000000000000000000000000000000000005f5e1000000000000000000000000000000000000000000000000000000000000000007596179537761700000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000035941590000000000000000000000000000000000000000000000000000000000";
 
-        let client = Client::new_from_env(Chain::Mainnet).unwrap();
+            let client = Client::new_from_env(Chain::Mainnet).unwrap();
 
-        let contract =
-            VerifyContract::new(address, contract.to_string(), compiler_version.to_string())
-                .constructor_arguments(Some(constructor_args))
-                .optimization(true)
-                .runs(200);
+            let contract =
+                VerifyContract::new(address, contract.to_string(), compiler_version.to_string())
+                    .constructor_arguments(Some(constructor_args))
+                    .optimization(true)
+                    .runs(200);
 
-        let _resp = client.submit_contract_verification(&contract).await;
+            let _resp = client.submit_contract_verification(&contract).await;
+        }).await
     }
 }
diff --git a/ethers-etherscan/src/gas.rs b/ethers-etherscan/src/gas.rs
index 4d3c66dd..7d4ce4d0 100644
--- a/ethers-etherscan/src/gas.rs
+++ b/ethers-etherscan/src/gas.rs
@@ -70,48 +70,61 @@ impl Client {
 
 #[cfg(test)]
 mod tests {
+    use std::time::Duration;
+
     use serial_test::serial;
 
     use ethers_core::types::Chain;
 
+    use crate::tests::run_at_least_duration;
+
     use super::*;
 
     #[tokio::test]
     #[serial]
     async fn gas_estimate_success() {
-        let client = Client::new_from_env(Chain::Mainnet).unwrap();
+        run_at_least_duration(Duration::from_millis(200), async {
+            let client = Client::new_from_env(Chain::Mainnet).unwrap();
 
-        let result = client.gas_estimate(2000000000u32.into()).await;
+            let result = client.gas_estimate(2000000000u32.into()).await;
 
-        assert!(result.is_ok());
+            assert!(result.is_ok());
+        })
+        .await
     }
 
     #[tokio::test]
     #[serial]
     async fn gas_estimate_error() {
-        let client = Client::new_from_env(Chain::Mainnet).unwrap();
+        run_at_least_duration(Duration::from_millis(200), async {
+            let client = Client::new_from_env(Chain::Mainnet).unwrap();
 
-        let err = client.gas_estimate(7123189371829732819379218u128.into()).await.unwrap_err();
+            let err = client.gas_estimate(7123189371829732819379218u128.into()).await.unwrap_err();
 
-        assert!(matches!(err, EtherscanError::GasEstimationFailed));
+            assert!(matches!(err, EtherscanError::GasEstimationFailed));
+        })
+        .await
     }
 
     #[tokio::test]
     #[serial]
     async fn gas_oracle_success() {
-        let client = Client::new_from_env(Chain::Mainnet).unwrap();
+        run_at_least_duration(Duration::from_millis(200), async {
+            let client = Client::new_from_env(Chain::Mainnet).unwrap();
 
-        let result = client.gas_oracle().await;
+            let result = client.gas_oracle().await;
 
-        assert!(result.is_ok());
+            assert!(result.is_ok());
 
-        let oracle = result.unwrap();
+            let oracle = result.unwrap();
 
-        assert!(oracle.safe_gas_price > 0);
-        assert!(oracle.propose_gas_price > 0);
-        assert!(oracle.fast_gas_price > 0);
-        assert!(oracle.last_block > 0);
-        assert!(oracle.suggested_base_fee > 0.0);
-        assert!(oracle.gas_used_ratio.len() > 0);
+            assert!(oracle.safe_gas_price > 0);
+            assert!(oracle.propose_gas_price > 0);
+            assert!(oracle.fast_gas_price > 0);
+            assert!(oracle.last_block > 0);
+            assert!(oracle.suggested_base_fee > 0.0);
+            assert!(oracle.gas_used_ratio.len() > 0);
+        })
+        .await
     }
 }
diff --git a/ethers-etherscan/src/lib.rs b/ethers-etherscan/src/lib.rs
index 689e8358..5d6e0701 100644
--- a/ethers-etherscan/src/lib.rs
+++ b/ethers-etherscan/src/lib.rs
@@ -78,8 +78,7 @@ impl Client {
             Chain::Mainnet | Chain::Ropsten | Chain::Kovan | Chain::Rinkeby | Chain::Goerli => {
                 std::env::var("ETHERSCAN_API_KEY")?
             }
-            Chain::XDai => String::default(),
-            chain => return Err(EtherscanError::ChainNotSupported(chain)),
+            _ => String::default(),
         };
         Self::new(chain, api_key)
     }
@@ -176,6 +175,11 @@ struct Query<'a, T: Serialize> {
 
 #[cfg(test)]
 mod tests {
+    use std::{
+        future::Future,
+        time::{Duration, SystemTime},
+    };
+
     use ethers_core::types::Chain;
 
     use crate::{Client, EtherscanError};
@@ -187,4 +191,12 @@ mod tests {
         assert!(matches!(err, EtherscanError::ChainNotSupported(_)));
         assert_eq!(err.to_string(), "chain XDai not supported");
     }
+
+    pub async fn run_at_least_duration(duration: Duration, block: impl Future) {
+        let start = SystemTime::now();
+        block.await;
+        if let Some(sleep) = duration.checked_sub(start.elapsed().unwrap()) {
+            tokio::time::sleep(sleep).await;
+        }
+    }
 }
diff --git a/ethers-etherscan/src/transaction.rs b/ethers-etherscan/src/transaction.rs
index 69b1564b..92df9d10 100644
--- a/ethers-etherscan/src/transaction.rs
+++ b/ethers-etherscan/src/transaction.rs
@@ -52,68 +52,82 @@ impl Client {
 
 #[cfg(test)]
 mod tests {
+    use std::time::Duration;
+
     use serial_test::serial;
 
-    use crate::Chain;
+    use crate::{tests::run_at_least_duration, Chain};
 
     use super::*;
 
     #[tokio::test]
     #[serial]
     async fn check_contract_execution_status_success() {
-        let client = Client::new_from_env(Chain::Mainnet).unwrap();
+        run_at_least_duration(Duration::from_millis(200), async {
+            let client = Client::new_from_env(Chain::Mainnet).unwrap();
 
-        let status = client
-            .check_contract_execution_status(
-                "0x16197e2a0eacc44c1ebdfddcfcfcafb3538de557c759a66e0ba95263b23d9007",
-            )
-            .await;
+            let status = client
+                .check_contract_execution_status(
+                    "0x16197e2a0eacc44c1ebdfddcfcfcafb3538de557c759a66e0ba95263b23d9007",
+                )
+                .await;
 
-        assert!(status.is_ok());
+            assert!(status.is_ok());
+        })
+        .await
     }
 
     #[tokio::test]
     #[serial]
     async fn check_contract_execution_status_error() {
-        let client = Client::new_from_env(Chain::Mainnet).unwrap();
+        run_at_least_duration(Duration::from_millis(200), async {
+            let client = Client::new_from_env(Chain::Mainnet).unwrap();
 
-        let err = client
-            .check_contract_execution_status(
-                "0x15f8e5ea1079d9a0bb04a4c58ae5fe7654b5b2b4463375ff7ffb490aa0032f3a",
-            )
-            .await
-            .unwrap_err();
+            let err = client
+                .check_contract_execution_status(
+                    "0x15f8e5ea1079d9a0bb04a4c58ae5fe7654b5b2b4463375ff7ffb490aa0032f3a",
+                )
+                .await
+                .unwrap_err();
 
-        assert!(matches!(err, EtherscanError::ExecutionFailed(_)));
-        assert_eq!(err.to_string(), "contract execution call failed: Bad jump destination");
+            assert!(matches!(err, EtherscanError::ExecutionFailed(_)));
+            assert_eq!(err.to_string(), "contract execution call failed: Bad jump destination");
+        })
+        .await
     }
 
     #[tokio::test]
     #[serial]
     async fn check_transaction_receipt_status_success() {
-        let client = Client::new_from_env(Chain::Mainnet).unwrap();
+        run_at_least_duration(Duration::from_millis(200), async {
+            let client = Client::new_from_env(Chain::Mainnet).unwrap();
 
-        let success = client
-            .check_transaction_receipt_status(
-                "0x513c1ba0bebf66436b5fed86ab668452b7805593c05073eb2d51d3a52f480a76",
-            )
-            .await;
+            let success = client
+                .check_transaction_receipt_status(
+                    "0x513c1ba0bebf66436b5fed86ab668452b7805593c05073eb2d51d3a52f480a76",
+                )
+                .await;
 
-        assert!(success.is_ok());
+            assert!(success.is_ok());
+        })
+        .await
     }
 
     #[tokio::test]
     #[serial]
     async fn check_transaction_receipt_status_failed() {
-        let client = Client::new_from_env(Chain::Mainnet).unwrap();
+        run_at_least_duration(Duration::from_millis(200), async {
+            let client = Client::new_from_env(Chain::Mainnet).unwrap();
 
-        let err = client
-            .check_transaction_receipt_status(
-                "0x21a29a497cb5d4bf514c0cca8d9235844bd0215c8fab8607217546a892fd0758",
-            )
-            .await
-            .unwrap_err();
+            let err = client
+                .check_transaction_receipt_status(
+                    "0x21a29a497cb5d4bf514c0cca8d9235844bd0215c8fab8607217546a892fd0758",
+                )
+                .await
+                .unwrap_err();
 
-        assert!(matches!(err, EtherscanError::TransactionReceiptFailed));
+            assert!(matches!(err, EtherscanError::TransactionReceiptFailed));
+        })
+        .await
     }
 }