diff --git a/.travis.yml b/.travis.yml
index 2047f62..e0cbb7f 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -43,18 +43,18 @@ script:
   - if [[ $TRAVIS_OS_NAME == "linux" && $TRAVIS_RUST_VERSION == "stable" ]]; then cargo clippy -- -D clippy::all; fi
   - cargo build --all
   - cargo build --examples
-  - if [[ $TRAVIS_OS_NAME == "linux" && $TRAVIS_RUST_VERSION == "nightly" ]]; then cargo doc --workspace --exclude tikv-client-proto --document-private-items --no-deps; fi
+  - if [[ $TRAVIS_OS_NAME == "linux" && $TRAVIS_RUST_VERSION == "nightly" ]]; then make doc; fi
   - if [[ $TRAVIS_RUST_VERSION == "nightly" ]]; then cargo test --all -- --nocapture; fi
   # For now we only run full integration tests on Linux. Here's why:
   # * Docker on OS X is not supported by Travis.
   # * Docker on Windows seems to not have the correct binary at `"/c/Program Files/Docker/Docker/DockerCli.exe" to switch it to Linux containers.
-  - if [[ $TRAVIS_OS_NAME == "linux" && $TRAVIS_RUST_VERSION == "nightly" ]]; then docker run -d --net=host --name pd --rm pingcap/pd --name "pd" --data-dir "pd" --client-urls "http://127.0.0.1:2379" --advertise-client-urls "http://127.0.0.1:2379"; fi
-  - if [[ $TRAVIS_OS_NAME == "linux" && $TRAVIS_RUST_VERSION == "nightly" ]]; then docker run -d --net=host --name kv --rm --ulimit nofile=90000:90000 pingcap/tikv --pd-endpoints "127.0.0.1:2379" --addr "127.0.0.1:2378" --data-dir "kv"; fi
+  - if [[ $TRAVIS_OS_NAME == "linux" && $TRAVIS_RUST_VERSION == "nightly" ]]; then make docker-pd; fi
+  - if [[ $TRAVIS_OS_NAME == "linux" && $TRAVIS_RUST_VERSION == "nightly" ]]; then make docker-kv; fi
   - if [[ $TRAVIS_OS_NAME == "linux" && $TRAVIS_RUST_VERSION == "nightly" ]]; then docker ps; fi
   - if [[ $TRAVIS_OS_NAME == "linux" && $TRAVIS_RUST_VERSION == "nightly" ]]; then docker logs pd; fi
   - if [[ $TRAVIS_OS_NAME == "linux" && $TRAVIS_RUST_VERSION == "nightly" ]]; then docker logs kv; fi
   - if [[ $TRAVIS_OS_NAME == "linux" && $TRAVIS_RUST_VERSION == "nightly" ]]; then sleep 60; fi
-  - if [[ $TRAVIS_OS_NAME == "linux" && $TRAVIS_RUST_VERSION == "nightly" ]]; then PD_ADDRS="127.0.0.1:2379" cargo test --all --features integration-tests -- --nocapture; fi
+  - if [[ $TRAVIS_OS_NAME == "linux" && $TRAVIS_RUST_VERSION == "nightly" ]]; then MULTI_REGION=1 make integration-test; fi
   - if [[ $TRAVIS_OS_NAME == "linux" && $TRAVIS_RUST_VERSION == "nightly" ]]; then cargo run --example raw -- --pd="127.0.0.1:2379"; fi
   - if [[ $TRAVIS_OS_NAME == "linux" && $TRAVIS_RUST_VERSION == "nightly" ]]; then cargo run --example transaction -- --pd="127.0.0.1:2379"; fi
   - if [[ $TRAVIS_OS_NAME == "linux" && $TRAVIS_RUST_VERSION == "nightly" ]]; then cargo run --example pessimistic -- --pd="127.0.0.1:2379"; fi
diff --git a/Cargo.toml b/Cargo.toml
index f3f9c34..c9904fc 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -23,7 +23,7 @@ derive-new = "0.5"
 fail = "0.4"
 futures = { version = "0.3", features = ["async-await", "thread-pool"] }
 futures-timer = "3.0"
-grpcio = { version = "0.8", features = [ "secure", "prost-codec", "use-bindgen" ], default-features = false }
+grpcio = { version = "0.8", features = [ "secure", "prost-codec", "use-bindgen", "openssl-vendored" ], default-features = false }
 lazy_static = "1"
 log = "0.4"
 prometheus = { version = "0.12", features = [ "push", "process" ], default-features = false } 
@@ -49,6 +49,8 @@ proptest-derive = "0.3"
 serial_test = "0.5.0"
 simple_logger = "1"
 tokio = { version = "1.0", features = [ "sync", "rt-multi-thread", "macros" ] }
+reqwest = {version = "0.11", default-features = false, features = ["native-tls-vendored"]}
+serde_json = "1"
 
 [workspace]
 members = [
diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..beef4e3
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,32 @@
+.PHONY: default check unit-test integration-tests test doc docker-pd docker-kv docker all
+
+default: check
+
+check:
+	cargo check --all
+	cargo fmt -- --check
+	cargo clippy -- -D clippy::all
+
+unit-test:
+	cargo test --all
+
+integration-test:
+# MULTI_REGION shall be set manually if needed
+	PD_ADDRS="127.0.0.1:2379" cargo test txn_ --all --features integration-tests -- --nocapture
+	PD_ADDRS="127.0.0.1:2379" cargo test raw_ --all --features integration-tests -- --nocapture
+	PD_ADDRS="127.0.0.1:2379" cargo test misc_ --all --features integration-tests -- --nocapture
+
+test: unit-test integration-test
+
+doc: 
+	cargo doc --workspace --exclude tikv-client-proto --document-private-items --no-deps
+
+docker-pd:
+	docker run -d -v $(shell pwd)/config:/config --net=host --name pd --rm pingcap/pd:latest --name "pd" --data-dir "pd" --client-urls "http://127.0.0.1:2379" --advertise-client-urls "http://127.0.0.1:2379" --config /config/pd.toml
+
+docker-kv:
+	docker run -d -v $(shell pwd)/config:/config --net=host --name kv --rm --ulimit nofile=90000:90000 pingcap/tikv:latest --pd-endpoints "127.0.0.1:2379" --addr "127.0.0.1:2378" --data-dir "kv" --config /config/tikv.toml
+
+docker: docker-pd docker-kv
+
+all: check doc test
diff --git a/config/pd.toml b/config/pd.toml
new file mode 100644
index 0000000..b6d78e9
--- /dev/null
+++ b/config/pd.toml
@@ -0,0 +1,3 @@
+[schedule]
+max-merge-region-size = 1
+max-merge-region-keys = 3
diff --git a/config/tikv.toml b/config/tikv.toml
new file mode 100644
index 0000000..bf00961
--- /dev/null
+++ b/config/tikv.toml
@@ -0,0 +1,10 @@
+[coprocessor]
+region-max-keys = 5
+region-split-keys = 3
+batch-split-limit = 100
+
+[raftstore]
+region-split-check-diff = "0KB"
+pd-heartbeat-tick-interval = "2s"
+pd-store-heartbeat-tick-interval = "5s"
+split-region-check-tick-interval = "1s"
\ No newline at end of file
diff --git a/src/pd/retry.rs b/src/pd/retry.rs
index 9dfc07b..ba42f60 100644
--- a/src/pd/retry.rs
+++ b/src/pd/retry.rs
@@ -25,7 +25,7 @@ use tokio::sync::RwLock;
 // FIXME: these numbers and how they are used are all just cargo-culted in, there
 // may be more optimal values.
 const RECONNECT_INTERVAL_SEC: u64 = 1;
-const MAX_REQUEST_COUNT: usize = 3;
+const MAX_REQUEST_COUNT: usize = 5;
 const LEADER_CHANGE_RETRY: usize = 10;
 
 /// Client for communication with a PD cluster. Has the facility to reconnect to the cluster.
diff --git a/src/util/iter.rs b/src/util/iter.rs
index d251e60..3c84e3b 100644
--- a/src/util/iter.rs
+++ b/src/util/iter.rs
@@ -74,7 +74,7 @@ mod test {
             .into_iter()
             .flat_map_ok(|i| Some(i).into_iter())
             .collect();
-        assert_eq!(result.unwrap(), vec![]);
+        assert_eq!(result.unwrap(), Vec::<i32>::new());
 
         let result: Result<Vec<i32>, ()> = vec![Result::<i32, ()>::Ok(0), Ok(1), Ok(2)]
             .into_iter()
diff --git a/tests/common/ctl.rs b/tests/common/ctl.rs
new file mode 100644
index 0000000..01046c6
--- /dev/null
+++ b/tests/common/ctl.rs
@@ -0,0 +1,28 @@
+// Copyright 2021 TiKV Project Authors. Licensed under Apache-2.0.
+//! The module provides some utility functions to control and get information
+//! from PD, using its HTTP API.
+
+use super::pd_addrs;
+use tikv_client_common::{Error, Result};
+
+pub async fn get_region_count() -> Result<u64> {
+    let res = reqwest::get(format!("http://{}/pd/api/v1/regions", pd_addrs()[0]))
+        .await
+        .map_err(|e| Error::StringError(e.to_string()))?;
+
+    let body = res
+        .text()
+        .await
+        .map_err(|e| Error::StringError(e.to_string()))?;
+    let value: serde_json::Value = serde_json::from_str(body.as_ref()).unwrap();
+    value["count"]
+        .as_u64()
+        .ok_or_else(|| Error::StringError("pd region count does not return an integer".to_owned()))
+}
+
+#[tokio::test]
+#[ignore]
+async fn test_get_region_count() -> Result<()> {
+    println!("{}", get_region_count().await?);
+    Ok(())
+}
diff --git a/tests/common/mod.rs b/tests/common/mod.rs
index e3a4730..1fb3f18 100644
--- a/tests/common/mod.rs
+++ b/tests/common/mod.rs
@@ -1,5 +1,13 @@
-use std::env;
-use tikv_client::{ColumnFamily, RawClient};
+mod ctl;
+
+use futures_timer::Delay;
+use log::{info, warn};
+use std::{env, time::Duration};
+use tikv_client::{ColumnFamily, Key, RawClient, Result, TransactionClient};
+
+const ENV_PD_ADDRS: &str = "PD_ADDRS";
+const ENV_ENABLE_MULIT_REGION: &str = "MULTI_REGION";
+const REGION_SPLIT_TIME_LIMIT: Duration = Duration::from_secs(15);
 
 // Delete all entries in TiKV to leave a clean space for following tests.
 pub async fn clear_tikv() {
@@ -14,7 +22,69 @@ pub async fn clear_tikv() {
     }
 }
 
-const ENV_PD_ADDRS: &str = "PD_ADDRS";
+// To test with multiple regions, prewrite some data. Tests that hope to test
+// with multiple regions should use keys in the corresponding ranges.
+pub async fn init() -> Result<()> {
+    // ignore SetLoggerError
+    let _ = simple_logger::SimpleLogger::new()
+        .with_level(log::LevelFilter::Warn)
+        .init();
+
+    if env::var(ENV_ENABLE_MULIT_REGION).is_ok() {
+        // 1000 keys: 0..1000
+        let keys_1 = std::iter::successors(Some(0u32), |x| Some(x + 1))
+            .take(1000)
+            .map(|x| x.to_be_bytes().to_vec());
+        // 1024 keys: 0..u32::MAX
+        let count = 1024;
+        let step = u32::MAX / count;
+        let keys_2 = std::iter::successors(Some(0u32), |x| Some(x + step))
+            .take(count as usize - 1)
+            .map(|x| x.to_be_bytes().to_vec());
+
+        ensure_region_split(keys_1.chain(keys_2), 100).await?;
+    }
+
+    clear_tikv().await;
+    Ok(())
+}
+
+async fn ensure_region_split(
+    keys: impl IntoIterator<Item = impl Into<Key>>,
+    region_count: u32,
+) -> Result<()> {
+    if ctl::get_region_count().await? as u32 >= region_count {
+        return Ok(());
+    }
+
+    // 1. write plenty transactional keys
+    // 2. wait until regions split
+
+    let client = TransactionClient::new(pd_addrs()).await?;
+    let mut txn = client.begin_optimistic().await?;
+    for key in keys.into_iter() {
+        txn.put(key.into(), vec![0, 0, 0, 0]).await?;
+    }
+    txn.commit().await?;
+    let mut txn = client.begin_optimistic().await?;
+    let _ = txn.scan(vec![].., 2048).await?;
+    txn.commit().await?;
+
+    info!("splitting regions...");
+    let start_time = std::time::Instant::now();
+    loop {
+        if ctl::get_region_count().await? as u32 >= region_count {
+            break;
+        }
+        if start_time.elapsed() > REGION_SPLIT_TIME_LIMIT {
+            warn!("Stop splitting regions: time limit exceeded");
+            break;
+        }
+        Delay::new(Duration::from_millis(200)).await;
+    }
+
+    Ok(())
+}
 
 pub fn pd_addrs() -> Vec<String> {
     env::var(ENV_PD_ADDRS)
diff --git a/tests/failpoint_tests.rs b/tests/failpoint_tests.rs
index 2e90613..90393ff 100644
--- a/tests/failpoint_tests.rs
+++ b/tests/failpoint_tests.rs
@@ -1,15 +1,15 @@
 #![cfg(feature = "integration-tests")]
 
 mod common;
-use common::{clear_tikv, pd_addrs};
+use common::{init, pd_addrs};
 use fail::FailScenario;
 use serial_test::serial;
 use tikv_client::{Result, TransactionClient, TransactionOptions};
 
 #[tokio::test]
 #[serial]
-async fn optimistic_heartbeat() -> Result<()> {
-    clear_tikv().await;
+async fn txn_optimistic_heartbeat() -> Result<()> {
+    init().await?;
     let scenario = FailScenario::setup();
     fail::cfg("after-prewrite", "sleep(10000)").unwrap();
 
diff --git a/tests/integration_tests.rs b/tests/integration_tests.rs
index 0b1d757..4a6cfd7 100644
--- a/tests/integration_tests.rs
+++ b/tests/integration_tests.rs
@@ -1,7 +1,18 @@
 #![cfg(feature = "integration-tests")]
 
+//! # Naming convention
+//!
+//! Test names should begin with one of the following:
+//! 1. txn_
+//! 2. raw_
+//! 3. misc_
+//!
+//! We make use of the convention to control the order of tests in CI, to allow
+//! transactional and raw tests to coexist, since transactional requests have
+//! requirements on the region boundaries.
+
 mod common;
-use common::{clear_tikv, pd_addrs};
+use common::{init, pd_addrs};
 use futures::prelude::*;
 use rand::{seq::IteratorRandom, thread_rng, Rng};
 use serial_test::serial;
@@ -20,7 +31,8 @@ const NUM_PEOPLE: u32 = 100;
 const NUM_TRNASFER: u32 = 100;
 
 #[tokio::test]
-async fn get_timestamp() -> Result<()> {
+#[serial]
+async fn txn_get_timestamp() -> Result<()> {
     const COUNT: usize = 1 << 8; // use a small number to make test fast
     let client = TransactionClient::new(pd_addrs()).await?;
 
@@ -40,8 +52,8 @@ async fn get_timestamp() -> Result<()> {
 // Tests transactional get, put, delete, batch_get
 #[tokio::test]
 #[serial]
-async fn crud() -> Result<()> {
-    clear_tikv().await;
+async fn txn_crud() -> Result<()> {
+    init().await?;
 
     let client = TransactionClient::new(pd_addrs()).await?;
     let mut txn = client.begin_optimistic().await?;
@@ -124,8 +136,8 @@ async fn crud() -> Result<()> {
 // Tests transactional insert and delete-your-writes cases
 #[tokio::test]
 #[serial]
-async fn insert_duplicate_keys() -> Result<()> {
-    clear_tikv().await;
+async fn txn_insert_duplicate_keys() -> Result<()> {
+    init().await?;
 
     let client = TransactionClient::new(pd_addrs()).await?;
     // Initialize TiKV store with {foo => bar}
@@ -148,8 +160,8 @@ async fn insert_duplicate_keys() -> Result<()> {
 
 #[tokio::test]
 #[serial]
-async fn pessimistic() -> Result<()> {
-    clear_tikv().await;
+async fn txn_pessimistic() -> Result<()> {
+    init().await?;
 
     let client = TransactionClient::new(pd_addrs()).await?;
     let mut txn = client.begin_pessimistic().await?;
@@ -167,7 +179,7 @@ async fn pessimistic() -> Result<()> {
 #[tokio::test]
 #[serial]
 async fn raw_bank_transfer() -> Result<()> {
-    clear_tikv().await;
+    init().await?;
     let client = RawClient::new(pd_addrs()).await?;
     let mut rng = thread_rng();
 
@@ -211,20 +223,15 @@ async fn raw_bank_transfer() -> Result<()> {
     Ok(())
 }
 
-/// Tests transactional API when there are multiple regions.
-/// Write large volumes of data to enforce region splitting.
-/// In order to test `scan`, data is uniformly inserted.
-// FIXME: this test is stupid. We should use pd-ctl or config files to make
-// multiple regions, instead of bulk writing.
 #[tokio::test]
 #[serial]
-async fn txn_write_million() -> Result<()> {
-    const NUM_BITS_TXN: u32 = 13;
+async fn txn_read() -> Result<()> {
+    const NUM_BITS_TXN: u32 = 4;
     const NUM_BITS_KEY_PER_TXN: u32 = 4;
     let interval = 2u32.pow(32 - NUM_BITS_TXN - NUM_BITS_KEY_PER_TXN);
     let value = "large_value".repeat(10);
 
-    clear_tikv().await;
+    init().await?;
     let client = TransactionClient::new(pd_addrs()).await?;
 
     for i in 0..2u32.pow(NUM_BITS_TXN) {
@@ -248,50 +255,49 @@ async fn txn_write_million() -> Result<()> {
         assert_eq!(res.count(), 2usize.pow(NUM_BITS_KEY_PER_TXN));
         txn.commit().await?;
     }
-    /* FIXME: scan all keys will make the message size exceed its limit
-       // test scan
-       let limit = 2u32.pow(NUM_BITS_KEY_PER_TXN + NUM_BITS_TXN + 2); // large enough
-       let snapshot = client.snapshot(
-           client.current_timestamp().await?,
-           TransactionOptions::default(),
-       );
-       let res = snapshot.scan(vec![].., limit).await?;
-       assert_eq!(res.count(), 2usize.pow(NUM_BITS_KEY_PER_TXN + NUM_BITS_TXN));
+    // test scan
+    let limit = 2u32.pow(NUM_BITS_KEY_PER_TXN + NUM_BITS_TXN + 2); // large enough
+    let mut snapshot = client.snapshot(
+        client.current_timestamp().await?,
+        TransactionOptions::default(),
+    );
+    let res = snapshot.scan(vec![].., limit).await?;
+    assert_eq!(res.count(), 2usize.pow(NUM_BITS_KEY_PER_TXN + NUM_BITS_TXN));
 
-       // scan by small range and combine them
-       let mut rng = thread_rng();
-       let mut keys = gen_u32_keys(200, &mut rng)
-           .iter()
-           .cloned()
-           .collect::<Vec<_>>();
-       keys.sort();
+    // scan by small range and combine them
+    let mut rng = thread_rng();
+    let mut keys = gen_u32_keys(200, &mut rng)
+        .iter()
+        .cloned()
+        .collect::<Vec<_>>();
+    keys.sort();
 
-       let mut sum = 0;
+    let mut sum = 0;
 
-       // empty key to key[0]
-       let snapshot = client.snapshot(
-           client.current_timestamp().await?,
-           TransactionOptions::default(),
-       );
-       let res = snapshot.scan(vec![]..keys[0].clone(), limit).await?;
-       sum += res.count();
+    // empty key to key[0]
+    let mut snapshot = client.snapshot(
+        client.current_timestamp().await?,
+        TransactionOptions::default(),
+    );
+    let res = snapshot.scan(vec![]..keys[0].clone(), limit).await?;
+    sum += res.count();
 
-       // key[i] .. key[i+1]
-       for i in 0..keys.len() - 1 {
-           let res = snapshot
-               .scan(keys[i].clone()..keys[i + 1].clone(), limit)
-               .await?;
-           sum += res.count();
-       }
+    // key[i] .. key[i+1]
+    for i in 0..keys.len() - 1 {
+        let res = snapshot
+            .scan(keys[i].clone()..keys[i + 1].clone(), limit)
+            .await?;
+        sum += res.count();
+    }
 
-       // keys[last] to unbounded
-       let res = snapshot.scan(keys[keys.len() - 1].clone().., limit).await?;
-       sum += res.count();
+    // keys[last] to unbounded
+    let res = snapshot.scan(keys[keys.len() - 1].clone().., limit).await?;
+    sum += res.count();
+
+    assert_eq!(sum, 2usize.pow(NUM_BITS_KEY_PER_TXN + NUM_BITS_TXN));
 
-       assert_eq!(sum, 2usize.pow(NUM_BITS_KEY_PER_TXN + NUM_BITS_TXN));
-    */
     // test batch_get and batch_get_for_update
-    const SKIP_BITS: u32 = 12; // do not retrieve all because there's a limit of message size
+    const SKIP_BITS: u32 = 0; // do not retrieve all because there's a limit of message size
     let mut cur = 0u32;
     let keys = iter::repeat_with(|| {
         let v = cur;
@@ -316,14 +322,15 @@ async fn txn_write_million() -> Result<()> {
 #[tokio::test]
 #[serial]
 async fn txn_bank_transfer() -> Result<()> {
-    clear_tikv().await;
+    init().await?;
     let client = TransactionClient::new(pd_addrs()).await?;
     let mut rng = thread_rng();
+    let options = TransactionOptions::new_optimistic()
+        .use_async_commit()
+        .drop_check(tikv_client::CheckLevel::Warn);
 
     let people = gen_u32_keys(NUM_PEOPLE, &mut rng);
-    let mut txn = client
-        .begin_with_options(TransactionOptions::new_optimistic())
-        .await?;
+    let mut txn = client.begin_with_options(options.clone()).await?;
     let mut sum: u32 = 0;
     for person in &people {
         let init = rng.gen::<u8>() as u32;
@@ -334,9 +341,7 @@ async fn txn_bank_transfer() -> Result<()> {
 
     // transfer
     for _ in 0..NUM_TRNASFER {
-        let mut txn = client
-            .begin_with_options(TransactionOptions::new_optimistic().use_async_commit())
-            .await?;
+        let mut txn = client.begin_with_options(options.clone()).await?;
         let chosen_people = people.iter().choose_multiple(&mut rng, 2);
         let alice = chosen_people[0];
         let mut alice_balance = get_txn_u32(&mut txn, alice.clone()).await?;
@@ -370,7 +375,7 @@ async fn txn_bank_transfer() -> Result<()> {
 #[tokio::test]
 #[serial]
 async fn raw_req() -> Result<()> {
-    clear_tikv().await;
+    init().await?;
     let client = RawClient::new(pd_addrs()).await?;
 
     // empty; get non-existent key
@@ -499,8 +504,8 @@ async fn raw_req() -> Result<()> {
 /// Only checks if we successfully update safepoint to PD.
 #[tokio::test]
 #[serial]
-async fn test_update_safepoint() -> Result<()> {
-    clear_tikv().await;
+async fn txn_update_safepoint() -> Result<()> {
+    init().await?;
     let client = TransactionClient::new(pd_addrs()).await?;
     let res = client.gc(client.current_timestamp().await?).await?;
     assert!(res);
@@ -508,19 +513,14 @@ async fn test_update_safepoint() -> Result<()> {
 }
 
 /// Tests raw API when there are multiple regions.
-/// Write large volumes of data to enforce region splitting.
-/// In order to test `scan`, data is uniformly inserted.
-///
-/// Ignoring this because we don't want to mess up transactional tests.
 #[tokio::test]
 #[serial]
-#[ignore]
 async fn raw_write_million() -> Result<()> {
-    const NUM_BITS_TXN: u32 = 9;
-    const NUM_BITS_KEY_PER_TXN: u32 = 10;
+    const NUM_BITS_TXN: u32 = 4;
+    const NUM_BITS_KEY_PER_TXN: u32 = 4;
     let interval = 2u32.pow(32 - NUM_BITS_TXN - NUM_BITS_KEY_PER_TXN);
 
-    clear_tikv().await;
+    init().await?;
     let client = RawClient::new(pd_addrs()).await?;
 
     for i in 0..2u32.pow(NUM_BITS_TXN) {
@@ -555,8 +555,8 @@ async fn raw_write_million() -> Result<()> {
         let _ = client
             .batch_scan(iter::repeat(vec![]..).take(batch_num), limit)
             .await?;
-        // FIXME: `each_limit` parameter does no work as expected.
-        // It limits the entries on each region of each rangqe, instead of each range.
+        // FIXME: `each_limit` parameter does no work as expected. It limits the
+        // entries on each region of each rangqe, instead of each range.
         // assert_eq!(res.len(), limit as usize * batch_num);
     }
 
@@ -565,11 +565,12 @@ async fn raw_write_million() -> Result<()> {
 
 #[tokio::test]
 #[serial]
-async fn pessimistic_rollback() -> Result<()> {
-    clear_tikv().await;
+async fn txn_pessimistic_rollback() -> Result<()> {
+    init().await?;
     let client = TransactionClient::new_with_config(pd_addrs(), Default::default()).await?;
     let mut preload_txn = client.begin_optimistic().await?;
     let key1 = vec![1];
+    let key2 = vec![2];
     let value = key1.clone();
 
     preload_txn.put(key1.clone(), value).await?;
@@ -582,27 +583,27 @@ async fn pessimistic_rollback() -> Result<()> {
         result?;
     }
 
-    // for _ in 0..100 {
-    //     let mut txn = client.begin_pessimistic().await?;
-    //     let result = txn
-    //         .batch_get_for_update(vec![key1.clone(), key2.clone()])
-    //         .await;
-    //     txn.rollback().await?;
-    //     let _ = result?;
-    // }
+    for _ in 0..100 {
+        let mut txn = client.begin_pessimistic().await?;
+        let result = txn
+            .batch_get_for_update(vec![key1.clone(), key2.clone()])
+            .await;
+        txn.rollback().await?;
+        let _ = result?;
+    }
 
     Ok(())
 }
 
 #[tokio::test]
 #[serial]
-async fn pessimistic_delete() -> Result<()> {
-    clear_tikv().await;
+async fn txn_pessimistic_delete() -> Result<()> {
+    init().await?;
     let client =
         TransactionClient::new_with_config(vec!["127.0.0.1:2379"], Default::default()).await?;
 
-    // The transaction will lock the keys and must release the locks on commit, even when values are
-    // not written to the DB.
+    // The transaction will lock the keys and must release the locks on commit,
+    // even when values are not written to the DB.
     let mut txn = client.begin_pessimistic().await?;
     txn.put(vec![1], vec![42]).await?;
     txn.delete(vec![1]).await?;
@@ -639,8 +640,8 @@ async fn pessimistic_delete() -> Result<()> {
 
 #[tokio::test]
 #[serial]
-async fn lock_keys() -> Result<()> {
-    clear_tikv().await;
+async fn txn_lock_keys() -> Result<()> {
+    init().await?;
     let client = TransactionClient::new_with_config(pd_addrs(), Default::default()).await?;
 
     let k1 = b"key1".to_vec();
@@ -673,8 +674,8 @@ async fn lock_keys() -> Result<()> {
 
 #[tokio::test]
 #[serial]
-async fn get_for_update() -> Result<()> {
-    clear_tikv().await;
+async fn txn_get_for_update() -> Result<()> {
+    init().await?;
     let client = TransactionClient::new_with_config(pd_addrs(), Default::default()).await?;
     let key1 = "key".to_owned();
     let key2 = "another key".to_owned();
@@ -717,8 +718,8 @@ async fn get_for_update() -> Result<()> {
 
 #[tokio::test]
 #[serial]
-async fn pessimistic_heartbeat() -> Result<()> {
-    clear_tikv().await;
+async fn txn_pessimistic_heartbeat() -> Result<()> {
+    init().await?;
 
     let key1 = "key1".to_owned();
     let key2 = "key2".to_owned();
@@ -759,7 +760,7 @@ async fn pessimistic_heartbeat() -> Result<()> {
 #[tokio::test]
 #[serial]
 async fn raw_cas() -> Result<()> {
-    clear_tikv().await;
+    init().await?;
     let client = RawClient::new(pd_addrs()).await?.with_atomic_for_cas();
     let key = "key".to_owned();
     let value = "value".to_owned();